nim-eth/eth/p2p/discoveryv5/hkdf.nim

31 lines
711 B
Nim

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