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()