31 lines
711 B
Nim
31 lines
711 B
Nim
import nimcrypto
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proc hkdf*(HashType: typedesc, ikm, salt, info: openArray[byte],
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output: var openArray[byte]) =
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var ctx: HMAC[HashType]
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ctx.init(salt)
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ctx.update(ikm)
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let prk = ctx.finish().data
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const hashLen = HashType.bits div 8
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var t: MDigest[HashType.bits]
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var numIters = output.len div hashLen
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if output.len mod hashLen != 0:
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inc numIters
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for i in 0 ..< numIters:
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ctx.init(prk)
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if i != 0:
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ctx.update(t.data)
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ctx.update(info)
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ctx.update([uint8(i + 1)])
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t = ctx.finish()
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let iStart = i * hashLen
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var sz = hashLen
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if iStart + sz >= output.len:
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sz = output.len - iStart
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copyMem(addr output[iStart], addr t.data, sz)
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ctx.clear()
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