diff --git a/docs/nbc_audit_2020/README.md b/docs/nbc_audit_2020/README.md
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+# NBC Audit 2020
+
+This folder contains the description, tasks and scope of Nimbus audit pre-mainnet launch.
+
+RFP:
+- https://our.status.im/nimbus-eth2-0-security-audit-request-for-proposal
+
+The audit was done in 3 phases, related branches are:
+- https://github.com/status-im/nimbus-eth2/tree/nbc-audit-2020-0
+- https://github.com/status-im/nimbus-eth2/tree/nbc-audit-2020-1
+- https://github.com/status-im/nimbus-eth2/tree/nbc-audit-2020-2
+
+The audit involved 3 vendors:
+- Consensys Diligence: https://consensys.net/diligence/
+- NCC: https://www.nccgroup.com/
+- Trail of Bits: https://www.trailofbits.com/
+
+Outline
+
+|                 Module                 |                   Repository                    | Audit round |           Category            |
+| -------------------------------------- | ----------------------------------------------- | ----------- | ----------------------------- |
+| Wire encryption                        | nim-crypto, nim-libp2p, nim-bearssl             | Round 1     | Network Core Audit            |
+| [Ethereum 2 Request/Response protocol](./eth2_spec_core/attestation_processing_and_production.md)   | nimbus-eth2, nim-faststreams, nim-serialization | Round 1     | Network Core Audit            |
+| [Discover Protocol (discv5)](./network_core/discovery_protocol_discv5.md)             | nim-eth                                         | Round 1     | Network Core Audit            |
+| [SSZ - (De)serialization & tree hashing](./network_core/ssz_serialization_and_tree_hashing.md) | nimbus-eth2                                     | Round 2     | Network Core Audit            |
+| [Block/attestation signing](./validator_core/block_attestation_signing.md)              | nimbus-eth2, nim-blscurve                       | Round 2     | Validator Core Audit         |
+| [Peer pool management](./eth2_spec_core/peer_pool_management.md)                   | nimbus-eth2                                     | Round 2     | ETH2 Specification Core Audit |
+| [Block Synchronization](./eth2_spec_core/block_synchronization.md)                  | nimbus-eth2                                     | Round 2     | ETH2 Specification Core Audit |
+| [Fork choice logic](./eth2_spec_core/fork_choice_logic.md)                      | nimbus-eth2                                     | Round 2     | ETH2 Specification Core Audit |
+| [Reward processing](./eth2_spec_core/reward_processing.md)                      | nimbus-eth2                                     | Round 2     | ETH2 Specification Core Audit |
+| [Eth1 data processing](./eth2_spec_core/eth1_data_processing.md)                  | nimbus-eth2, nim-web3                           | Round 2     | ETH2 Specification Core Audit |
+| [Epoch finalisation and justification](./eth2_spec_core/epoch_finalization_and_justification.md)  | nimbus-eth2                                     | Round 2     | ETH2 Specification Core Audit |
+| [Signature verification](./eth2_spec_core/signature_verification.md)                 | nimbus-eth2, nim-blscurve                       | Round 2     | ETH2 Specification Core Audit |
+| [State transition logic](./eth2_spec_core/state_transition_logic.md)                 | nimbus-eth2                                     | Round 2     | ETH2 Specification Core Audit |
+| [Publish/Subscribe protocol (gossipsub)](./network_core/publish_subscribe_gossipsub.md) | nim-libp2p                                      | Round 4     | Network Core Audit            |
+| [Command Line Interface (CLI)](./validator_core/command_line_interface_CLI.md)           | nimbus-eth2, nim-confutils                      | Round 3     | Validator Core Audit         |
+| [RPC API](./validator_core/rpc_api.md)                                | nimbus-eth2, nim-json-rpc                       | Round 3     | Validator Core Audit         |
+| [Accounts management & key storage](./validator_core/account_management_and_key_storage.md)      | nimbus-eth2                                     | Round 3     | Validator Core Audit         |
+| [Slash-prevention mechanisms](./validator_core/slash_prevention_mechanisms.md)            | nimbus-eth2                                     | Round 3     | Validator Core Audit         |
+| [Attestation processing and production](./eth2_spec_core/attestation_processing_and_production.md) | nimbus-eth2                                     | Round 3     | ETH2 Specification Core Audit |
+| [Block processing and production](./eth2_spec_core/block_processing_and_production.md)        | nimbus-eth2                                     | Round 3     | ETH2 Specification Core Audit |
diff --git a/docs/nbc_audit_2020/eth2_spec_core/attestation_processing_and_production.md b/docs/nbc_audit_2020/eth2_spec_core/attestation_processing_and_production.md
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+---
+title: "Attestation Processing & production"
+code_owner: "(tersec) and Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 3"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Related readings:
+
+- Honest validator spec: [https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md](https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md)
+- Deposit contract spec: [https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/deposit-contract.md](https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/deposit-contract.md)
+
+## 0. Clarification of Scope
+
+There is a slight overlap between Trail of Bits tasks and NCC tasks in this round
+
+Trail of Bits will be in charge of the high-level attestation/block processing and production.
+
+This relies on BLS signatures and so secret keys which are under NCC scope.
+
+Concretely:
+- NCC scope [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim)
+- Trail of Bits scope:
+
+  - [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim)
+
+  - [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim)
+
+## 1. State after round 2
+
+- Crypto.nim and nim-blscurve dependencies were audited by NCC in phase 1:
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/crypto.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/crypto.nim)
+
+- signatures.nim and dependencies which handles signature and verification were audited as well
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/signatures.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/signatures.nim)
+
+## 2. Explanation of the application flow
+
+The main application is the **beacon_node**, it has 2 mode of operations regarding accounts. With accounts managed in an integrated manner or managed in a split manner, something we call the VC/BN split (Validator Client / Beacon Node split).
+
+In both case, there is a need of a keystore to hold the validators' **signing keys.**
+
+### 2.1 Reminder on Ethereum secret keys
+
+As a reminder, the best explanation for the 2 kinds of secret keys (signing keys and **withdrawal keys**) used in Ethereum 2.0 is at [https://blog.ethereum.org/2020/05/21/keys/](https://blog.ethereum.org/2020/05/21/keys/).
+
+#### Risks
+
+A Beacon Node only requires the signing key which presents the following risks: someone who get holds of a signing keys can sign blocks and attestations, leading to double-signing and slashing. The slashing penalty is about 1 ETH (from the initial 32 ETH) but you are ejected when you reach below 16 ETH. An attacker cannot get your funds
+
+### 2.2 Validation in Nimbus
+
+2.2.1 ***Case: No Validator Client split***
+
+**#### This part will be audited by Trail of Bits**
+
+Every start of a slot (every 12 seconds), "onSlotStart" will be scheduled: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L986-L987](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L986-L987)
+
+This will call "[handleValidator](https://github.com/status-im/nim-beacon-chain/blob/a84a8ba192e2f4c7bae22470b44b2db12f95ab0f/beacon_chain/beacon_node.nim#L516)Duties": [https://github.com/status-im/nim-beacon-chain/blob/a84a8ba192e2f4c7bae22470b44b2db12f95ab0f/beacon_chain/beacon_node.nim#L516](https://github.com/status-im/nim-beacon-chain/blob/a84a8ba192e2f4c7bae22470b44b2db12f95ab0f/beacon_chain/beacon_node.nim#L516)
+
+Then we get in the validator_duties.nim file which is the main consumer of the keystore: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L439-L440](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L439-L440)
+
+In particular when signing attestations:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L146](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L146)
+
+and blocks:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L295](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L295)
+
+**#### This part will be audited by NCC**
+
+The block and attestation signing functions need access to the secret keys and they are isolated in validator_pool.nim [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim)
+
+The AttachedValidator type is an abstraction over having the secret key in-memory or in a separate process:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node_types.nim#L73-L94](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node_types.nim#L73-L94)
+
+2.2.2 ***Case: With Validator Client split*
+
+A nbc-audit-2020-2 will be tagged with the** **validator client split.
+****
+
+**#### This part will be audited by Trail of Bits**
+
+When there is a VC/BN split, the Validator Client logic mirrors the main BeaconNode with an onSlotStart [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L102](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L102)
+
+Note: validator_client.nim is a stand-alone application
+
+**#### This part will be audited by NCC (in validator_pool.nim)**
+
+And signing block and attestations calls the same function as the no-split case:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L168](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L168)
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L144](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L144)
+
+with implementation in [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/block_processing_and_production.md b/docs/nbc_audit_2020/eth2_spec_core/block_processing_and_production.md
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+++ b/docs/nbc_audit_2020/eth2_spec_core/block_processing_and_production.md
@@ -0,0 +1,9 @@
+---
+title: "Block Processing & production"
+code_owner: "(tersec) and Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 3"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+See [attestation_processing_and_production.md](./attestation_processing_and_production.md)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/block_synchronization.md b/docs/nbc_audit_2020/eth2_spec_core/block_synchronization.md
new file mode 100644
index 000000000..e2aeb111a
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/block_synchronization.md
@@ -0,0 +1,31 @@
+---
+title: "Block synchronization"
+code_owner: "Eugene Kabanov (cheatfate)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+**Note:** Currently there is an issue where ingoing block sync is slow on Medalla testnet and being investigated. There are many changes being made.
+
+Spec: TODO
+
+# Ingoing Sync algorithms
+
+*syncing from remote peers*
+
+We have 2 kinds of ingoing sync, forward sync and backward sync
+
+forward sync:
+
+[https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_manager.nim](https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_protocol.nim)
+
+backward sync:
+
+[https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/request_manager.nim](https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/request_manager.nim)
+
+# Outgoing Sync algorithms
+
+*remote peers sync from us*
+
+[https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_protocol.nim](https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_protocol.nim)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/epoch_finalization_and_justification.md b/docs/nbc_audit_2020/eth2_spec_core/epoch_finalization_and_justification.md
new file mode 100644
index 000000000..a0caeeba3
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/epoch_finalization_and_justification.md
@@ -0,0 +1,19 @@
+---
+title: "Epoch finalization and justification"
+code_owner: "Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Spec: [https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#justification-and-finalization](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#justification-and-finalization)
+
+Visual depiction: [https://github.com/protolambda/eth2-docs#justification-and-finalization](https://github.com/protolambda/eth2-docs#justification-and-finalization)
+
+![finalization.png](./finalization.png)
+
+Implementation: [https://github.com/status-im/nim-beacon-chain/blob/543cbdfc6b9bc16f0331df2797422b7dc4d61eeb/beacon_chain/spec/state_transition_epoch.nim#L102-L240](https://github.com/status-im/nim-beacon-chain/blob/543cbdfc6b9bc16f0331df2797422b7dc4d61eeb/beacon_chain/spec/state_transition_epoch.nim#L102-L240)
+
+Self-test: [https://github.com/status-im/nim-beacon-chain/blob/master/tests/spec_epoch_processing/test_process_justification_and_finalization.nim](https://github.com/status-im/nim-beacon-chain/blob/master/tests/spec_epoch_processing/test_process_justification_and_finalization.nim)
+
+EF test vectors: [https://github.com/status-im/nim-beacon-chain/blob/543cbdfc/tests/official/test_fixture_state_transition_epoch.nim#L57-L58](https://github.com/status-im/nim-beacon-chain/blob/543cbdfc6b9bc16f0331df2797422b7dc4d61eeb/tests/official/test_fixture_state_transition_epoch.nim#L57-L58)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/eth1_data_processing.md b/docs/nbc_audit_2020/eth2_spec_core/eth1_data_processing.md
new file mode 100644
index 000000000..4e59c127f
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/eth1_data_processing.md
@@ -0,0 +1,26 @@
+---
+title: "ETH1 data processing"
+code_owner: ""
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain, nim-web3"
+---
+
+ETH2 validators are added by locking ETH on a designated ETH1 contract.
+
+Monitoring the ETH1 deposit contract is done via the mainchain_monitor service
+which connects to a ETH1 Web3 provider (Geth or Infura):
+- [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/mainchain_monitor.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/mainchain_monitor.nim)
+- Spec of the deposit contract (for reference): [https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/deposit-contract.md](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/deposit-contract.md)
+
+nim-web3 scope is significantly larger (and unimplemented) that the audit of nim-beacon-chain. The subset in scope is the one used by mainchain_monitor namely:
+
+- The types Web3, Sender, Subscription
+
+- The procedures
+
+  - eth_getBlockByHash, eth_getBlockByNumber
+
+Processing the new entrants is done in the following state_transition function:
+- [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition_block.nim#L125-L130](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition_block.nim#L125-L130)
+- Specced at [https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#eth1-data](https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#eth1-data)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/finalization.png b/docs/nbc_audit_2020/eth2_spec_core/finalization.png
new file mode 100644
index 000000000..ae5ba6336
Binary files /dev/null and b/docs/nbc_audit_2020/eth2_spec_core/finalization.png differ
diff --git a/docs/nbc_audit_2020/eth2_spec_core/fork_choice_logic.md b/docs/nbc_audit_2020/eth2_spec_core/fork_choice_logic.md
new file mode 100644
index 000000000..aad6862e0
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/fork_choice_logic.md
@@ -0,0 +1,35 @@
+---
+title: "Fork choice logic"
+code_owner: "Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Fork choice backend:
+- [https://github.com/status-im/nim-beacon-chain/tree/devel/beacon_chain/fork_choice](https://github.com/status-im/nim-beacon-chain/tree/devel/beacon_chain/fork_choice)
+
+Fork choice is provided by the "attestation_pool" when "select_head" is called
+
+- [https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/attestation_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/attestation_pool.nim)
+
+Tests:
+- [https://github.com/status-im/nim-beacon-chain/tree/master/tests/fork_choice](https://github.com/status-im/nim-beacon-chain/tree/master/tests/fork_choice)
+
+- [https://github.com/status-im/nim-beacon-chain/blob/master/tests/test_attestation_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/master/tests/test_attestation_pool.nim)
+
+Specs:
+- [https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/fork-choice.md](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/fork-choice.md)
+
+- Explainer from Prysmatic: [https://hackmd.io/bABJiht3Q9SyV3Ga4FT9lQ?view](https://hackmd.io/bABJiht3Q9SyV3Ga4FT9lQ?view)
+
+Paper:
+- Combining GHOST and Casper
+  Vitalik Buterin, Diego Hernandez, Thor Kamphefner, Khiem Pham, Zhi Qiao, Danny Ryan, Juhyeok Sin, Ying Wang, Yan X Zhang
+  [https://arxiv.org/abs/2003.03052](https://arxiv.org/abs/2003.03052)
+
+(Short) Implementations
+
+- [https://github.com/ethereum/research/blob/master/ghost/ghost.py](https://github.com/ethereum/research/blob/master/ghost/ghost.py)
+- Original Proto-array (in Go): [https://github.com/protolambda/lmd-ghost/blob/master/eth2/fork_choice/choices/proto_array/proto_array.go](https://github.com/protolambda/lmd-ghost/blob/master/eth2/fork_choice/choices/proto_array/proto_array.go)
+- Proto-array incorporating Lighthouse updates: [https://github.com/protolambda/eth2-py-hacks/blob/master/proto_array.py](https://github.com/protolambda/eth2-py-hacks/blob/master/proto_array.py)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/peer_pool_management.md b/docs/nbc_audit_2020/eth2_spec_core/peer_pool_management.md
new file mode 100644
index 000000000..7e10ccf8d
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/peer_pool_management.md
@@ -0,0 +1,19 @@
+---
+title: "Peer pool management"
+code_owner: "Eugene Kabanov (cheatfate)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Note: no spec
+
+location:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/peer_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/peer_pool.nim)
+
+Created Issues from round 1:
+
+- [https://github.com/status-im/nim-beacon-chain/issues/1365](https://github.com/status-im/nim-beacon-chain/issues/1365)
+- [https://github.com/status-im/nim-beacon-chain/issues/1364](https://github.com/status-im/nim-beacon-chain/issues/1364)
+- [https://github.com/status-im/nim-beacon-chain/issues/1362](https://github.com/status-im/nim-beacon-chain/issues/1362)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/reward_processing.md b/docs/nbc_audit_2020/eth2_spec_core/reward_processing.md
new file mode 100644
index 000000000..09de9519c
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/reward_processing.md
@@ -0,0 +1,36 @@
+---
+title: "Reward processing"
+code_owner: "(tersec)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Spec: [https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md](https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md)
+Code: [https://github.com/status-im/nim-beacon-chain/blob/bc6eefe3/beacon_chain/spec/state_transition_epoch.nim#L242-L440](https://github.com/status-im/nim-beacon-chain/blob/bc6eefe31ec60a7a1740b444e5c132fa55b4e859/beacon_chain/spec/state_transition_epoch.nim#L242-L440)
+
+Test: Missing ! For a long-time rewards and penalties tests were missing and they have not been integrated in NBC [https://github.com/status-im/nim-beacon-chain/blame/bc6eefe3/tests/official/test_fixture_state_transition_epoch.nim#L60-L63](https://github.com/status-im/nim-beacon-chain/blame/bc6eefe31ec60a7a1740b444e5c132fa55b4e859/tests/official/test_fixture_state_transition_epoch.nim#L60-L63)
+
+Fuzzing: Missing ! ([https://github.com/sigp/beacon-fuzz](https://github.com/sigp/beacon-fuzz))
+
+Note: an unclear rewards/penalties spec led to non-finalization in the very first testnet Schlesi.
+
+Improvement in the spec test suite: [https://github.com/ethereum/eth2.0-specs/pull/1747](https://github.com/ethereum/eth2.0-specs/pull/1747)
+
+Writeup:
+
+*However, around 11 AM UTC on May 15th , it had been observed that Schlesi had
+been nearly 50 epochs away from finality. While the initial cause of the finality delay has not been ascertained, they’re not rare in a test
+network where participants are not obligated/incentivized to keep their
+validators running. The lack of finality eventually lead to instability
+in the chain, causing several temporary forks in the network.*
+
+![schlesi_rewards.png](./schlesi_rewards.png)
+
+*The block tree at the time of no finality.*
+
+*After almost 300 epochs of no finality, there was a block that split the
+chain between Lighthouse and Prysm at slot 150496. A block was submitted that had an attester slashing, which surfaced differences in how all
+clients tally rewards and penalties for slashed validators. This
+revealed 2 different penalty calculation bugs in Prysm! After this chain split, it was decided that the best course of action would be to
+restart with a fresh slate.*
diff --git a/docs/nbc_audit_2020/eth2_spec_core/schlesi_rewards.png b/docs/nbc_audit_2020/eth2_spec_core/schlesi_rewards.png
new file mode 100644
index 000000000..e046cdaae
Binary files /dev/null and b/docs/nbc_audit_2020/eth2_spec_core/schlesi_rewards.png differ
diff --git a/docs/nbc_audit_2020/eth2_spec_core/signature_verification.md b/docs/nbc_audit_2020/eth2_spec_core/signature_verification.md
new file mode 100644
index 000000000..fd1fda717
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/signature_verification.md
@@ -0,0 +1,25 @@
+---
+title: "Signature verification"
+code_owner: "Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain, nim-blscurve"
+---
+
+# Description
+
+Verify that cryptographic primitives (Miracl and BLST) are properly used at a high-level.
+We assume that they are correctly implemented in the backend.
+
+Specs:
+- [https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#bls-signatures](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#bls-signatures)
+
+For information, evaluation of backends: [https://notes.status.im/nim-bls-curve-backends](https://notes.status.im/nim-bls-curve-backends)
+
+# Links
+
+Links to the repositories and more information
+
+- [https://github.com/status-im/nim-blscurve](https://github.com/status-im/nim-blscurve) (low-level wrapper over crypto primitives, 2 backends)
+- [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/crypto.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/crypto.nim) (high-level BLS signature types and serialization)
+- [https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/spec/signatures.nim](https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/spec/signatures.nim) (abstraction over signing and verification of consensus objects)
diff --git a/docs/nbc_audit_2020/eth2_spec_core/state_transition.png b/docs/nbc_audit_2020/eth2_spec_core/state_transition.png
new file mode 100644
index 000000000..956f67a79
Binary files /dev/null and b/docs/nbc_audit_2020/eth2_spec_core/state_transition.png differ
diff --git a/docs/nbc_audit_2020/eth2_spec_core/state_transition_logic.md b/docs/nbc_audit_2020/eth2_spec_core/state_transition_logic.md
new file mode 100644
index 000000000..413479ef5
--- /dev/null
+++ b/docs/nbc_audit_2020/eth2_spec_core/state_transition_logic.md
@@ -0,0 +1,37 @@
+---
+title: "State transition logic"
+code_owner: "(tersec)"
+round: "Audit round 2"
+category: "ETH2 Specification Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Spec: [https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function)
+
+Annotated spec from Vitalik: [https://github.com/ethereum/annotated-spec/blob/master/phase0/beacon-chain.md](https://github.com/ethereum/annotated-spec/blob/master/phase0/beacon-chain.md)
+Annotated spec from Ben (from Consensys): [https://benjaminion.xyz/eth2-annotated-spec/phase0/beacon-chain](https://benjaminion.xyz/eth2-annotated-spec/phase0/beacon-chain)
+
+Visual depiction: [https://github.com/protolambda/eth2-docs#phase-0-beaconstate-transition](https://github.com/protolambda/eth2-docs#phase-0-beaconstate-transition)
+
+![state_transition.png](./state_transition.png)
+
+Implementation:
+- block: [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition_block.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition.nim)
+- epoch: [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition_epoch.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition.nim)
+- High-level API: [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition.nim) and [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition_helpers.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/state_transition.nim)
+Implementation follows the spec closely with an additional caching mechanism that avoids recomputing epoch invariants.
+
+Tests:
+- Ethereum Foundation vectors are loaded here: [https://github.com/status-im/nim-beacon-chain/tree/master/tests/official](https://github.com/status-im/nim-beacon-chain/tree/master/tests/official)
+- Self-tests were added for attestations, deposits and justification/finalization
+  - [https://github.com/status-im/nim-beacon-chain/tree/master/tests/spec_block_processing](https://github.com/status-im/nim-beacon-chain/tree/master/tests/spec_block_processing)
+  - [https://github.com/status-im/nim-beacon-chain/tree/master/tests/spec_epoch_processing](https://github.com/status-im/nim-beacon-chain/tree/master/tests/spec_epoch_processing)
+
+Fuzzing via [https://github.com/sigp/beacon-fuzz](https://github.com/sigp/beacon-fuzz) covers:
+- attestation
+- attester_slashing
+- state transition for block
+- deposit
+- proposer slashing
+- shuffling
+- voluntary exit
diff --git a/docs/nbc_audit_2020/network_core/discovery_protocol_discv5.md b/docs/nbc_audit_2020/network_core/discovery_protocol_discv5.md
new file mode 100644
index 000000000..04b2f2d20
--- /dev/null
+++ b/docs/nbc_audit_2020/network_core/discovery_protocol_discv5.md
@@ -0,0 +1,18 @@
+---
+title: "Discovery Protocol (discv5)"
+code_owner: ""
+round: "Audit round 1"
+category: "Network Core Audit"
+repositories: "nim-eth"
+---
+
+## Discovery “discv5”
+
+- Protocol specification: [https://github.com/ethereum/devp2p/tree/master/discv5](https://github.com/ethereum/devp2p/tree/master/discv5)
+- Note: the wire format might change ([https://github.com/ethereum/devp2p/issues/152](https://github.com/ethereum/devp2p/issues/152))
+- Part of `nim-eth` repository that holds the discovery v5 code: [https://github.com/status-im/nim-eth/tree/master/eth/p2p/discoveryv5](https://github.com/status-im/nim-eth/tree/master/eth/p2p/discoveryv5)
+- In scope:
+    - All of `discoveryv5` directory
+    - All other modules in the `nim-eth` repository that the discoveryv5 code depends on, namely: `keys`, `rlp`, `async_utils`. It currently is also depending on and `trie/db` but as this is to be replaced, it can be considered out-of-scope.
+- For additional information see also the [readme](https://github.com/status-im/nim-eth/blob/master/doc/discv5.md).
+- [Open issues](https://github.com/status-im/nim-eth/issues?q=is%3Aissue+is%3Aopen+label%3Adiscoveryv5) and those that are likely to have [security implications](https://github.com/status-im/nim-eth/issues?q=is%3Aissue+is%3Aopen+label%3Adiscoveryv5+label%3Asecurity).
diff --git a/docs/nbc_audit_2020/network_core/eth2_req_resp_protocol.md b/docs/nbc_audit_2020/network_core/eth2_req_resp_protocol.md
new file mode 100644
index 000000000..0ad803a7a
--- /dev/null
+++ b/docs/nbc_audit_2020/network_core/eth2_req_resp_protocol.md
@@ -0,0 +1,31 @@
+---
+title: "Ethereum 2 Request/Response protocol"
+code_owner: "Zahary Karadjov (zah)"
+round: "Audit round 1"
+category: "Network Core Audit"
+repositories: "nim-beacon-chain, nim-faststreams, nim-serialization"
+---
+
+The Eth2 Requests/Response protocols are specified here:
+https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/p2p-interface.md
+
+Within nim-beacon-chain, we have a single module implementing the spec:
+https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/eth2_network.nim
+
+The implementation sits on top of our LibP2P library:
+https://github.com/status-im/nim-libp2p
+
+At the moment, Ethereum 2 defines a single high-level protocol based on the spec (the Beacon chain syncing protocol). Our implementation of this protocol can be found here:
+https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_protocol.nim
+https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_manager.nim
+
+Certain parts of the protocol implementation are procedurally generated through Nim's compile-time code generation features (i.e. macros). This is similar to using a RPC framework such as Apache Thrift or gRPC and the primary motivation is avoiding the manual writing of tedious and error-prone message serialization code. As a convenience, the build system provides an always up-to-date snapshot of the generated code here:
+https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/sync_protocol.nim.generated.nim
+
+The generated code should be easy to read and I recommend focusing the review on it, but if studying the generator is also of interest, it can be found here:
+https://github.com/status-im/nim-eth/blob/master/eth/p2p/p2p_protocol_dsl.nim
+
+Further explanations and more detailed rationale can be found here:
+https://github.com/status-im/nim-beacon-chain/wiki/The-macro-skeptics-guide-to-the-p2pProtocol-macro
+
+Network flow outline: https://github.com/status-im/nim-beacon-chain/wiki/networking-flow
diff --git a/docs/nbc_audit_2020/network_core/publish_subscribe_gossipsub.md b/docs/nbc_audit_2020/network_core/publish_subscribe_gossipsub.md
new file mode 100644
index 000000000..75f4f5c3b
--- /dev/null
+++ b/docs/nbc_audit_2020/network_core/publish_subscribe_gossipsub.md
@@ -0,0 +1,44 @@
+---
+title: "Publish/Subscribe protocol (gossipsub)"
+code_owner: "Giovanni Petrantoni (sinkingsugar)"
+round: "Audit round 4"
+category: "Network Core Audit"
+repositories: "nim-libp2p"
+---
+
+Seems that gossipsub might not be ready for Round 1 : libp2p/gossipsub1.1
+
+Base spec here: [https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/gossipsub-v1.0.md](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/gossipsub-v1.0.md)
+
+Gossip 1.1 here: [https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/gossipsub-v1.1.md](https://github.com/libp2p/specs/blob/master/pubsub/gossipsub/gossipsub-v1.1.md)
+
+Published paper: [https://arxiv.org/pdf/2007.02754.pdf](https://arxiv.org/pdf/2007.02754.pdf)
+
+Gossip 1.1 is basically sitting on top of 1.0 so both specs knowledge is kind of necessary.
+
+### Code hot paths and major importance points
+
+Publishing:
+
+[https://github.com/status-im/nim-libp2p/blob/d75cc6edcaf1ebcb422d3f42633f58cde6a62592/libp2p/protocols/pubsub/gossipsub.nim#L1153](https://github.com/status-im/nim-libp2p/blob/d75cc6edcaf1ebcb422d3f42633f58cde6a62592/libp2p/protocols/pubsub/gossipsub.nim#L1153)
+
+RPC management: (within that we have validation, relevant for NBC)
+
+[https://github.com/status-im/nim-libp2p/blob/d75cc6edcaf1ebcb422d3f42633f58cde6a62592/libp2p/protocols/pubsub/gossipsub.nim#L1024](https://github.com/status-im/nim-libp2p/blob/d75cc6edcaf1ebcb422d3f42633f58cde6a62592/libp2p/protocols/pubsub/gossipsub.nim#L1024)
+
+Maintenance heartbeat:
+
+[https://github.com/status-im/nim-libp2p/blob/d75cc6edcaf1ebcb422d3f42633f58cde6a62592/libp2p/protocols/pubsub/gossipsub.nim#L737](https://github.com/status-im/nim-libp2p/blob/d75cc6edcaf1ebcb422d3f42633f58cde6a62592/libp2p/protocols/pubsub/gossipsub.nim#L737)
+
+----------------------------------------------------------------
+
+here's a list of issues files for this workpackage:
+
+https://github.com/status-im/nimbus-eth2/issues/1885
+https://github.com/status-im/nimbus-eth2/issues/1878
+https://github.com/status-im/nimbus-eth2/issues/1877
+https://github.com/status-im/nimbus-eth2/issues/1876
+https://github.com/status-im/nimbus-eth2/issues/1875
+https://github.com/status-im/nimbus-eth2/issues/1874
+https://github.com/status-im/nimbus-eth2/issues/1873
+https://github.com/status-im/nimbus-eth2/issues/1871
diff --git a/docs/nbc_audit_2020/network_core/ssz_serialization_and_tree_hashing.md b/docs/nbc_audit_2020/network_core/ssz_serialization_and_tree_hashing.md
new file mode 100644
index 000000000..467796e0e
--- /dev/null
+++ b/docs/nbc_audit_2020/network_core/ssz_serialization_and_tree_hashing.md
@@ -0,0 +1,46 @@
+---
+title: "SSZ (De)Serialization & Tree hashing"
+code_owner: "Zahary Karadjov (zah)"
+round: "Audit round 2"
+category: "Network Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+Relevant modules:
+
+SSZ spec implementation:
+https://github.com/status-im/nim-beacon-chain/tree/master/beacon_chain/ssz
+
+Spec:
+https://github.com/ethereum/eth2.0-specs/blob/dev/ssz/simple-serialize.md
+
+Lower-level layers:
+
+* Nim-serialization
+https://github.com/status-im/nim-serialization/
+Implements compile-time reflection responsible for operations such as "List all serializable fields of an object", defines a generic protocol and a set of extensibility points (overloadable functions) that can be used to provide custom serialization for certain types.
+
+May be sensitive to bugs in the Nim compiler related to generic programming.
+
+* Nim-FastStreams
+https://github.com/status-im/nim-faststreams/
+Defines low-level interfaces for working with various synchronous and asynchronous input streams.
+
+The SSZ implementation is tested against the official Eth2 test suite here:
+https://github.com/status-im/nim-beacon-chain/blob/master/tests/official/test_fixture_ssz_consensus_objects.nim
+https://github.com/status-im/nim-beacon-chain/blob/master/tests/official/test_fixture_ssz_generic_types.nim
+
+Run the tests with:
+nim c -r tests/official/test_fixture_ssz_consensus_objects.nim
+
+Also, with some basic fuzzing tests here:
+https://github.com/status-im/nim-beacon-chain/blob/master/scripts/run_ssz_fuzzing_test.nims
+https://github.com/status-im/nim-beacon-chain/blob/master/tests/fuzzing/ssz_fuzzing.nim
+
+The fuzzing tests can be launched with:
+
+nim scripts/run_ssz_fuzzing_test.nims Attestation
+
+or
+
+nim scripts/run_ssz_fuzzing_test.nims --fuzzer:honggfuz Attestation
diff --git a/docs/nbc_audit_2020/validator_core/account_management_and_key_storage.md b/docs/nbc_audit_2020/validator_core/account_management_and_key_storage.md
new file mode 100644
index 000000000..e62ef226f
--- /dev/null
+++ b/docs/nbc_audit_2020/validator_core/account_management_and_key_storage.md
@@ -0,0 +1,221 @@
+---
+title: "Account Management & Key storage"
+code_owner: "Zahary Karadjov (zah) & Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 3"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+
+Related readings:
+
+- Honest validator spec: [https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md](https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md)
+- Deposit contract spec: [https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/deposit-contract.md](https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/deposit-contract.md)
+- Explanation of signing and withdrawal keys: [https://blog.ethereum.org/2020/05/21/keys/](https://blog.ethereum.org/2020/05/21/keys/)
+- Keystore EIP2386: [https://github.com/ethereum/EIPs/blob/4494da0966afa7318ec0157948821b19c4248805/EIPS/eip-2386.md](https://github.com/ethereum/EIPs/blob/4494da0966afa7318ec0157948821b19c4248805/EIPS/eip-2386.md)
+- Key Derivation EIP2333: [https://eips.ethereum.org/EIPS/eip-2333](https://eips.ethereum.org/EIPS/eip-2333)
+
+A validator will do a deposit of 32 ETH to participate in proof of stake. Each secret key control 32 ETH, a single beacon node can handle hundreds to thousands of validators and so the same amount of secret keys.
+
+## 0. Scope clarification
+
+Beyond the signing and withdrawal keys, another type of keys is used in the application called "Network private keys". Those are application instance specific not user-specific and are used for P2P identity (secp256k1 secret keys), they do not secure money.
+
+They were reviewed as part of [https://github.com/status-im/nim-beacon-chain/issues/1320](https://github.com/status-im/nim-beacon-chain/issues/1320)
+
+and so are out of scope. See [https://github.com/status-im/nim-beacon-chain/pull/1533/files#diff-f64593cb13697c7f93a225b3b01a5921](https://github.com/status-im/nim-beacon-chain/pull/1533/files#diff-f64593cb13697c7f93a225b3b01a5921) to have an idea of where they are used
+
+## 1. State after round 2
+
+- Crypto.nim and nim-blscurve dependencies were audited by NCC in phase 1:
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/crypto.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/crypto.nim)
+
+- signatures.nim and dependencies which handles signature and verification were audited as well
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/signatures.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/signatures.nim)
+
+## 2. Explanation of the application flow
+
+The main application is the **beacon_node**, it has 2 mode of operations regarding accounts. With accounts managed in an integrated manner or managed in a split manner, something we call the VC/BN split (Validator Client / Beacon Node split).
+
+In both case, there is a need of a keystore to hold the validators' **signing keys.**
+
+### 2.1 Reminder on Ethereum secret keys
+
+As a reminder, the best explanation for the 2 kinds of secret keys (signing keys and **withdrawal keys**) used in Ethereum 2.0 is at [https://blog.ethereum.org/2020/05/21/keys/](https://blog.ethereum.org/2020/05/21/keys/).
+
+#### Risks
+
+A Beacon Node only requires the signing key which presents the following risks: someone who get holds of a signing keys can sign blocks and attestations, leading to double-signing and slashing. The slashing penalty is about 1 ETH (from the initial 32 ETH) but you are ejected when you reach below 16 ETH. An attacker cannot get your funds
+
+### 2.2 Validation in Nimbus
+
+2.2.1 ***Case: No Validator Client split***
+
+**#### This part will be audited by Trail of Bits**
+
+Every start of a slot (every 12 seconds), "onSlotStart" will be scheduled: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L986-L987](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L986-L987)
+
+This will call "[handleValidator](https://github.com/status-im/nim-beacon-chain/blob/a84a8ba192e2f4c7bae22470b44b2db12f95ab0f/beacon_chain/beacon_node.nim#L516)Duties": [https://github.com/status-im/nim-beacon-chain/blob/a84a8ba192e2f4c7bae22470b44b2db12f95ab0f/beacon_chain/beacon_node.nim#L516](https://github.com/status-im/nim-beacon-chain/blob/a84a8ba192e2f4c7bae22470b44b2db12f95ab0f/beacon_chain/beacon_node.nim#L516)
+
+Then we get in the validator_duties.nim file which is the main consumer of the keystore: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L439-L440](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L439-L440)
+
+In particular when signing attestations:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L146](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L146)
+
+and blocks:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L295](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L295)
+
+**#### This part will be audited by NCC**
+
+The block and attestation signing functions need access to the secret keys and they are isolated in validator_pool.nim [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim)
+
+The AttachedValidator type is an abstraction over having the secret key in-memory or in a separate process:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node_types.nim#L73-L94](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node_types.nim#L73-L94)
+
+2.2.2 ***Case: With Validator Client split*
+
+A nbc-audit-2020-2 will be tagged with the** **validator client split.
+****
+
+**#### This part will be audited by Trail of Bits**
+
+When there is a VC/BN split, the Validator Client logic mirrors the main BeaconNode with an onSlotStart [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L102](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L102)
+
+Note: validator_client.nim is a stand-alone application
+
+**#### This part will be audited by NCC (in validator_pool.nim)**
+
+And signing block and attestations calls the same function as the no-split case:
+
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L168](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L168)
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L144](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim#L144)
+
+with implementation in [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim)
+
+2.2.3 ***Side-note on hardening***
+
+We plan to make signing in a separate process ([https://github.com/status-im/nim-beacon-chain/issues/545](https://github.com/status-im/nim-beacon-chain/issues/545)) whether the Beacon Node and Validator Client are split or integrated.
+
+This was introduced in [https://github.com/status-im/nim-beacon-chain/pull/1522/files](https://github.com/status-im/nim-beacon-chain/pull/1522/files)
+which adds a signing_process.nim file - it is a separate binary and for now the BN (or potentially the VC) talks to it through stdin/stdout to give it roots to sign and it echoes back the signed result.
+
+a nbc-audit-2020-2 branch which will have this PR will be tagged before the start of the audit
+
+Further hardening may consist of:
+
+- a hardened memory allocator [https://github.com/status-im/nim-beacon-chain/issues/563](https://github.com/status-im/nim-beacon-chain/issues/563)
+- non-dumpable memory and encrypted memory: [https://github.com/status-im/nim-beacon-chain/issues/545](https://github.com/status-im/nim-beacon-chain/issues/545)
+
+## 3. Deposits creation
+
+Besides validation, deposits creation also involves keys, keystore and wallets.
+
+This is done in a dedicated binary `deposit_contract.nim`
+which in particular asks for user private keys [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/deposit_contract.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/deposit_contract.nim)
+
+and creates the directory for each validator and their wallet and mnemonic private keys
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/deposit_contract.nim#L173](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/deposit_contract.nim#L173)
+
+The reference implementation is [https://github.com/ethereum/eth2.0-deposit-cli](https://github.com/ethereum/eth2.0-deposit-cli)
+
+User instructions are at: [https://status-im.github.io/nim-beacon-chain/create_wallet_and_deposit.html](https://status-im.github.io/nim-beacon-chain/create_wallet_and_deposit.html)
+
+#### Related audits
+
+Trail of Bits audit of the Ethereum Foundation deposit contract [https://github.com/ethereum/eth2.0-deposit-cli/issues?q=is%3Aissue+is%3Aopen+ToB+Audit](https://github.com/ethereum/eth2.0-deposit-cli/issues?q=is%3Aissue+is%3Aopen+ToB+Audit)
+
+## 3. Key management
+
+### 3.1 Loading the keys
+
+Keys are loaded in-memory by everything that calls `addLocalValidator` and `addLocalValidators` [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L44-L61](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L44-L61)
+
+Namely, on BeaconNode init: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L291](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L291)
+Note: the out of process signing will be tagged later, see devel code: [https://github.com/status-im/nim-beacon-chain/blob/697bd23c/beacon_chain/beacon_node.nim#L280-L286](https://github.com/status-im/nim-beacon-chain/blob/697bd23c9bbdc76470d6ed1a01260c34617f60bd/beacon_chain/beacon_node.nim#L280-L286)
+
+The `validatorKeys` iterator which returns the validators secret signing keys is defined in `keystore_management.nim` [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/keystore_management.nim#L71-L93](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/keystore_management.nim#L71-L93)
+
+### 3.2 Saving keys
+
+The keys are saved in the following situations:
+
+- After the deposits process we provide: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/deposit_contract.nim#L179-L185](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/deposit_contract.nim#L179-L185)
+- When someone stakes through the official Ethereum 2 launchpad: [https://medalla.launchpad.ethereum.org/](https://medalla.launchpad.ethereum.org/)
+- When someone uses a third-party that happen to use Nimbus in the backend, typically a stacking pool or an exchange
+- When keys are migrated from one client to the next, on both import or export.
+
+The `saveValidatorKey` procedure is a leftover of refactoring [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L37-L42](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L37-L42)
+
+### 3.3 Keystore & Wallet implementation
+
+EIP2386 [https://github.com/ethereum/EIPs/blob/4494da0966afa7318ec0157948821b19c4248805/EIPS/eip-2386.md](https://github.com/ethereum/EIPs/blob/4494da0966afa7318ec0157948821b19c4248805/EIPS/eip-2386.md) is implemented in [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/keystore.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/spec/keystore.nim)
+
+EIP2333 for key derivation [https://eips.ethereum.org/EIPS/eip-2333](https://eips.ethereum.org/EIPS/eip-2333) is implemented in [https://github.com/status-im/nim-blscurve/blob/master/blscurve/eth2_keygen/eth2_keygen.nim](https://github.com/status-im/nim-blscurve/blob/master/blscurve/eth2_keygen/eth2_keygen.nim)
+
+The `keystore.nim` has references to related spec EIP2334 and BIP39
+
+UUID generation implementation is in [https://github.com/status-im/nim-eth/blob/master/eth/keyfile/uuid.nim](https://github.com/status-im/nim-eth/blob/master/eth/keyfile/uuid.nim) (already audited?)
+
+Importing keystores and keymanagement as explained to users:
+
+- import keystore link
+- [https://status-im.github.io/nim-beacon-chain/medalla.html#key-management](https://status-im.github.io/nim-beacon-chain/medalla.html#key-management)
+
+## 4. Configuring Secrets
+
+Secrets are configured in `conf.nim` [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim)
+
+In particular:
+
+- validatorsDirFlag: "A directory containing validator keystores"
+- secretsDirFlag: "A directory containing validator keystore passwords"
+- walletsDirFlag: "A directory containing wallet files"
+- validators: "Path to a validator keystore"
+- inProcessValidators: "Disable the push model (the beacon node tells a signing process with the private keys of the validators what to sign and when) and load the validators in the beacon node itself". Actually the keys are currently loaded in-process by default (and not in the signing_process binary) but that should change in the future and then this switch will make sense.
+
+Everything related to wallets and generating/signing validator deposits:
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim#L259-L324](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim#L259-L324)
+
+Also impacting secrets is the nonInteractive flag as it will be used by people handling more than a couple of keys.
+
+CLI audit is in Consensys Diligence scope.
+
+### 5. Testing the APIs that handle secrets
+
+TODO, scripts to easily try the following scenarios
+1. Launch a testnet
+2. Join with an extra validator by passing credentials via
+
+- wallets
+- commandline
+- keystores
+
+3. Import 100 new validators
+
+4. Export 100 validators to use in another client
+
+ And/or use the Medalla testnet:
+
+- provide ETH1 secret keys to go through the deposit process
+- provide ETH2 keystore.json and/or mnemonic to go through their importing in Nimbus
+
+      This is to avoid waiting a day due to ETH1_FOLLOW_DISTANCE to become a ETH2 validator
+
+User instructions to import a keystore:
+
+- [https://status-im.github.io/nim-beacon-chain/medalla.html#3-import-keystores](https://status-im.github.io/nim-beacon-chain/medalla.html#3-import-keystores)
+- [https://status-im.github.io/nim-beacon-chain/medalla.html#key-management](https://status-im.github.io/nim-beacon-chain/medalla.html#key-management)
+- Base files: [https://github.com/status-im/nim-beacon-chain/tree/nbc-audit-2020-1/docs/the_nimbus_book/src](https://github.com/status-im/nim-beacon-chain/tree/nbc-audit-2020-1/docs/the_nimbus_book/src)
+
+For now (for Nimbus to implement the script)
+
+- modifying the launch local testnet script [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim#L259-L324](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim#L259-L324)
+    - deposits: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/scripts/launch_local_testnet.sh#L182-L188](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/scripts/launch_local_testnet.sh#L182-L188)
+    - launching a node with its validators and their secret: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/scripts/launch_local_testnet.sh#L311-L316](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/scripts/launch_local_testnet.sh#L311-L316)
diff --git a/docs/nbc_audit_2020/validator_core/block_attestation_signing.md b/docs/nbc_audit_2020/validator_core/block_attestation_signing.md
new file mode 100644
index 000000000..485a03254
--- /dev/null
+++ b/docs/nbc_audit_2020/validator_core/block_attestation_signing.md
@@ -0,0 +1,38 @@
+---
+title: "Block/attestation signing"
+code_owner: "Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 2"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain"
+---
+
+# Description
+
+Verify that cryptographic primitives (Miracl and BLST) are properly used at a high-level.
+We assume that they are correctly implemented in the backend. Note, for this phase 2 we are concerned about the proper usage internal to nim-beacon-chain. Phase 3 will be about the end-user API (keystores and secret management).
+
+Specs:
+- [https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#bls-signatures](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/beacon-chain.md#bls-signatures)
+
+For information, evaluation of backends: [https://notes.status.im/nim-bls-curve-backends](https://notes.status.im/nim-bls-curve-backends)
+
+(phase 3) ETH2 has 2 kinds of keys
+- a signing key which is used by validators to sign attestations or blocks.
+The signing key is needed on a permanent basis by the validator client (audit phase 3).
+Leaking this key puts the owner at risk of slashing (double-voting)
+- a withdrawal key which is used by validators to retrieve their stake (~32 ETH).
+The withdrawal key should be generated offline and stored offline.
+Doc: [https://blog.ethereum.org/2020/05/21/keys/](https://blog.ethereum.org/2020/05/21/keys/)
+
+# Links
+
+Links to the repositories and more information
+
+- [https://github.com/status-im/nim-blscurve](https://github.com/status-im/nim-blscurve) (low-level wrapper over crypto primitives, 2 backends)
+- [https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/crypto.nim](https://github.com/status-im/nim-beacon-chain/blob/master/beacon_chain/spec/crypto.nim) (high-level BLS signature types and serialization)
+- [https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/spec/signatures.nim](https://github.com/status-im/nim-beacon-chain/blob/devel/beacon_chain/spec/signatures.nim) (abstraction over signing and verification of consensus objects)
+- [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_pool.nim) (Pool of validators, currently includes secret keys in process)
+    - For information (not merged, not to be audited), PR to separate the key in another process: [https://github.com/status-im/nim-beacon-chain/pull/1522](https://github.com/status-im/nim-beacon-chain/pull/1522)
+- High-level callers of signing primitives (for round 3 "validators"):
+    - [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim)
+    - [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_client.nim)
diff --git a/docs/nbc_audit_2020/validator_core/command_line_interface_CLI.md b/docs/nbc_audit_2020/validator_core/command_line_interface_CLI.md
new file mode 100644
index 000000000..9613325d8
--- /dev/null
+++ b/docs/nbc_audit_2020/validator_core/command_line_interface_CLI.md
@@ -0,0 +1,51 @@
+---
+title: "Command Line Interface (CLI)"
+code_owner: "Zahary Karadjov (zah)"
+round: "Audit round 3"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain, nim-confutils"
+---
+
+## Goals
+
+- Ensure that the CLI can handle malicious inputs (overflow, unicode, invalid characters, ...)
+- Prevent users from shooting themselves in the foot:
+    - Avoid losing data
+    - Avoid losing funds/secrets (overlap with NCC work on secrets acknowledged, more eyes on this critical part is welcome)
+    - Clear instructions:
+        - The book [https://status-im.github.io/nim-beacon-chain/](https://status-im.github.io/nim-beacon-chain/)
+        - Audit freeze: [https://github.com/status-im/nim-beacon-chain/tree/nbc-audit-2020-1/docs/the_nimbus_book/src](https://github.com/status-im/nim-beacon-chain/tree/nbc-audit-2020-1/docs/the_nimbus_book/src)
+- With a focus on the workflow to stake ETH
+    - See the book
+    - [https://medalla.launchpad.ethereum.org/](https://medalla.launchpad.ethereum.org/)
+
+## Code
+
+- All conf options: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/conf.nim)
+- Makefile with preset build/run configuration: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/Makefile](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/Makefile)
+
+The key binaries with a CLI are:
+
+- beacon_node.nim which is configured by the BeaconConf type
+and can be compiled with `make beacon_node`
+- validator_client.nim which is configured by `make validator_client`
+- deposit_contract.nim which allows to make a ETH1 deposit
+
+## Secret keys
+
+TODO
+
+- Address with Goerli ETH to test the deposit contract and ETH2 keystore generation
+- ETH2 validator enabled on Medalla to test the beacon_node / validator_client
+
+## Related audit reports
+
+Trail of bits audit of the Ethereum Foundation deposit contract:
+
+- [https://github.com/ethereum/eth2.0-deposit-cli/issues?q=is%3Aissue+is%3Aopen+ToB+Audit](https://github.com/ethereum/eth2.0-deposit-cli/issues?q=is%3Aissue+is%3Aopen+ToB+Audit)
+
+----------------------------------------------------------------
+
+https://github.com/status-im/nim-beacon-chain/issues/1320 ← also relevant for walletfile generation (even though the file is encrypted and usually in an ACL protected subpath (userdir); but its world readable + may leak info about wallets)
+
+https://github.com/status-im/nim-beacon-chain/issues/1687
diff --git a/docs/nbc_audit_2020/validator_core/rpc_api.md b/docs/nbc_audit_2020/validator_core/rpc_api.md
new file mode 100644
index 000000000..4e1aef5b3
--- /dev/null
+++ b/docs/nbc_audit_2020/validator_core/rpc_api.md
@@ -0,0 +1,30 @@
+---
+title: "RPC API"
+code_owner: ""
+round: "Audit round 3"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain, nim-json_rpc"
+---
+
+RPC resources:
+
+- Official mandatory APIs: [https://ethereum.github.io/eth2.0-APIs/](https://ethereum.github.io/eth2.0-APIs/)
+* OpenAPI description: [https://ethereum.github.io/eth2.0-APIs/beacon-node-oapi.yaml](https://ethereum.github.io/eth2.0-APIs/beacon-node-oapi.yaml)
+
+Code:
+
+- RpcServer in [https://github.com/status-im/nim-json-rpc](https://github.com/status-im/nim-json-rpc)
+- Validator API handlers: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_api.nim#L177](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_api.nim#L177)
+- init: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L259-L262](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L259-L262)
+- Beacon Node API handlers: [https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L715-L833](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/beacon_node.nim#L715-L833)
+
+----------------------------------------------------------------
+
+https://github.com/status-im/nim-json-rpc/issues/81
+
+https://github.com/status-im/nim-beacon-chain/issues/1653
+https://github.com/status-im/nim-beacon-chain/issues/1652
+https://github.com/status-im/nim-beacon-chain/issues/1651
+https://github.com/status-im/nim-beacon-chain/issues/1650
+
+recommendations/observations: [https://github.com/status-im/nim-beacon-chain/issues/1665](https://github.com/status-im/nim-beacon-chain/issues/1665)
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+---
+title: "Slash Prevention Mechanisms"
+code_owner: "Mamy André-Ratsimbazafy (mratsim)"
+round: "Audit round 3"
+category: "Validator Core Audit"
+repositories: "nim-beacon-chain"
+---
+Note: Slashing Protection is a very new feature and not merged/enabled by default yet in the codebase.
+
+For the moment it leaves in the PR: [https://github.com/status-im/nim-beacon-chain/pull/1643](https://github.com/status-im/nim-beacon-chain/pull/1643)
+
+----------------------
+
+## Resources
+
+### Overview of slashing and how it ties in with the rest of Eth2.0
+
+Phase 0 for humans - Validator responsibilities:
+
+- https://notes.ethereum.org/@djrtwo/Bkn3zpwxB#Validator-responsibilities
+
+Phase 0 spec - Honest Validator - how to avoid slashing
+
+- https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#how-to-avoid-slashing
+
+### In-depth reading on slashing conditions
+
+- Detecting slashing conditions https://hackmd.io/@n0ble/By897a5sH
+- Open issue on writing a slashing detector https://github.com/ethereum/eth2.0-pm/issues/63
+- Casper the Friendly Finality Gadget, Vitalik Buterin and Virgil Griffith
+https://arxiv.org/pdf/1710.09437.pdf
+Figure 2
+An individual validator ν MUST NOT publish two distinct votes,〈ν,s1,t1,h(s1),h(t1) AND〈ν,s2,t2,h(s2),h(t2),
+such that either:
+I. h(t1) = h(t2). Equivalently, a validator MUST NOT publish two distinct votes for the same target height.
+
+     OR
+     II. h(s1) < h(s2) < h(t2) < h(t1).
+     Equivalently, a validator MUST NOT vote within the span of its other votes.
+
+- Vitalik's annotated spec: https://github.com/ethereum/annotated-spec/blob/d8c51af84f9f309d91c37379c1fcb0810bc5f10a/phase0/beacon-chain.md#proposerslashing
+1. A proposer can get slashed for signing two distinct headers at the same slot.
+2. An attester can get slashed for signing
+two attestations that together violate the Casper FFG slashing conditions.
+- https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/validator.md#ffg-vote
+- The "source" is the current_justified_epoch
+- The "target" is the current_epoch
+
+### Reading on weak subjectivity
+
+- https://notes.ethereum.org/@adiasg/weak-subjectvity-eth2
+- https://www.symphonious.net/2019/11/27/exploring-ethereum-2-weak-subjectivity-period/
+- https://ethresear.ch/t/weak-subjectivity-under-the-exit-queue-model/5187
+
+### Reading of interop serialization format
+
+- Import/export format: https://hackmd.io/@sproul/Bk0Y0qdGD
+- Tests: https://github.com/eth2-clients/slashing-protection-interchange-tests
+
+## Implementation
+
+In `validator_slashing_protection.nim` (TODO merge PR and tag an audit branch)
+and used in `validator_duties.nim`  (no VC/BN split) or `validator_clients.nim` (with Validator Client/Beacon Node split)
+
+For slashing protection (in contrast to slashing detection) we only care about our own validators. We also assume that before signing a block or an attestation, the node is "synced" to the chain, i.e. it knows last finalized epoch of the whole blockchain.
+
+The `isSynced` function has a naive heuristic for now and will be changed in the future to properly handle weak subjectivity period.
+
+[https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L87-L111](https://github.com/status-im/nim-beacon-chain/blob/nbc-audit-2020-1/beacon_chain/validator_duties.nim#L87-L111)