BIP0340_CHALLENGE
ret = _bip0340_hash((const u8*)BIP0340_CHALLENGE, sizeof(BIP0340_CHALLENGE) - 1,
ret = _bip0340_hash((const u8*)BIP0340_CHALLENGE, sizeof(BIP0340_CHALLENGE) - 1,
ret = _bip0340_hash((const u8*)BIP0340_CHALLENGE, sizeof(BIP0340_CHALLENGE) - 1,
ret = _bip0340_hash((const u8*)BIP0340_CHALLENGE, sizeof(BIP0340_CHALLENGE) - 1,