75 lines
2.4 KiB
Nim
75 lines
2.4 KiB
Nim
# beacon_chain
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# Copyright (c) 2018-2020 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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# Serenity hash function / digest
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#
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# https://github.com/ethereum/eth2.0-specs/blob/v0.12.1/specs/phase0/beacon-chain.md#hash
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#
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# In Phase 0 the beacon chain is deployed with SHA256 (SHA2-256).
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# Note that is is different from Keccak256 (often mistakenly called SHA3-256)
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# and SHA3-256.
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#
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# In Eth1.0, the default hash function is Keccak256 and SHA256 is available as a precompiled contract.
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#
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# In our code base, to enable a smooth transition
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# (already did Blake2b --> Keccak256 --> SHA2-256),
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# we call this function `eth2digest`, and it outputs a `Eth2Digest`. Easy to sed :)
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{.push raises: [Defect].}
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import
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chronicles,
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nimcrypto/[sha2, hash],
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stew/byteutils,
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hashes,
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eth/common/eth_types_json_serialization
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export
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hash.`$`, sha2, readValue, writeValue
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type
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Eth2Digest* = MDigest[32 * 8] ## `hash32` from spec
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Eth2Hash* = sha256 ## Context for hash function
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func shortLog*(x: Eth2Digest): string =
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x.data[0..3].toHex()
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chronicles.formatIt Eth2Digest:
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shortLog(it)
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# TODO: expose an in-place digest function
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# when hashing in loop or into a buffer
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# See: https://github.com/cheatfate/nimcrypto/blob/b90ba3abd/nimcrypto/sha2.nim#L570
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func eth2digest*(v: openArray[byte]): Eth2Digest {.inline.} =
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# We use the init-update-finish interface to avoid
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# the expensive burning/clearing memory (20~30% perf)
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# TODO: security implication?
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var ctx: sha256
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ctx.init()
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ctx.update(v)
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ctx.finish()
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func update*(ctx: var Sha2Context; digest: Eth2Digest) =
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ctx.update digest.data
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template withEth2Hash*(body: untyped): Eth2Digest =
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## This little helper will init the hash function and return the sliced
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## hash:
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## let hashOfData = withHash: h.update(data)
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var h {.inject.}: sha256
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init(h)
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body
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finish(h)
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func hash*(x: Eth2Digest): Hash =
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## Hash for digests for Nim hash tables
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# Stub for BeaconChainDB
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# We just slice the first 4 or 8 bytes of the block hash
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# depending of if we are on a 32 or 64-bit platform
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result = cast[ptr Hash](unsafeAddr x)[]
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