def xsubkey

bend-collections@1.0.0.0 · spec/crypto/chacha.bend:196

import Base

196# Section 2.3: XChaCha20 is ChaCha20 under the HChaCha20 subkey of the
197# first 16 nonce bytes, with the nonce 0x00000000 || nonce[16..24].
198def xsubkey(+key: List<&2, U32>, +nonce: List<&2, U32>) -> List<&2, U32>:
199  hchacha20(key, prefix(16n, nonce))