nimbus-eth2/beacon_chain/spec/digest.nim

110 lines
3.3 KiB
Nim

# beacon_chain
# Copyright (c) 2018-2020 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
# Serenity hash function / digest
#
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.3/specs/phase0/beacon-chain.md#hash
#
# In Phase 0 the beacon chain is deployed with SHA256 (SHA2-256).
# Note that is is different from Keccak256 (often mistakenly called SHA3-256)
# and SHA3-256.
#
# In Eth1.0, the default hash function is Keccak256 and SHA256 is available as a precompiled contract.
#
# In our code base, to enable a smooth transition
# (already did Blake2b --> Keccak256 --> SHA2-256),
# we call this function `eth2digest`, and it outputs a `Eth2Digest`. Easy to sed :)
{.push raises: [Defect].}
import
# Standard library
std/hashes,
#Status libraries
chronicles,
nimcrypto/[sha2, hash],
stew/byteutils,
hashes,
eth/common/eth_types_json_serialization,
blscurve
export
hash.`$`, sha2, readValue, writeValue
type
Eth2Digest* = MDigest[32 * 8] ## `hash32` from spec
when BLS_BACKEND == BLST:
export blscurve.update
type Eth2DigestCtx* = BLST_SHA256_CTX
else:
type Eth2DigestCtx* = sha2.sha256
func shortLog*(x: Eth2Digest): string =
x.data.toOpenArray(0, 3).toHex()
chronicles.formatIt Eth2Digest:
shortLog(it)
# TODO: expose an in-place digest function
# when hashing in loop or into a buffer
# See: https://github.com/cheatfate/nimcrypto/blob/b90ba3abd/nimcrypto/sha2.nim#L570
func eth2digest*(v: openArray[byte]): Eth2Digest {.noInit.} =
## Apply the Eth2 Hash function
## Do NOT use for secret data.
when BLS_BACKEND == BLST:
# BLST has a fast assembly optimized SHA256
result.data.bls_sha256_digest(v)
else:
# We use the init-update-finish interface to avoid
# the expensive burning/clearing memory (20~30% perf)
var ctx: Eth2DigestCtx
ctx.init()
ctx.update(v)
ctx.finish()
when BLS_BACKEND == BLST:
func update*(ctx: var BLST_SHA256_CTX; digest: Eth2Digest) =
ctx.update digest.data
func update*(ctx: var sha256; digest: Eth2Digest) =
ctx.update digest.data
template withEth2Hash*(body: untyped): Eth2Digest =
## This little helper will init the hash function and return the sliced
## hash:
## let hashOfData = withHash: h.update(data)
when nimvm:
# In SSZ, computeZeroHashes require compile-time SHA256
block:
var h {.inject.}: sha256
init(h)
body
finish(h)
else:
when BLS_BACKEND == BLST:
block:
var h {.inject, noInit.}: Eth2DigestCtx
init(h)
body
var res {.noInit.}: Eth2Digest
finalize(res.data, h)
res
else:
block:
var h {.inject, noInit.}: Eth2DigestCtx
init(h)
body
finish(h)
func hash*(x: Eth2Digest): Hash =
## Hash for digests for Nim hash tables
# Stub for BeaconChainDB
# We just slice the first 4 or 8 bytes of the block hash
# depending of if we are on a 32 or 64-bit platform
result = cast[ptr Hash](unsafeAddr x)[]