I’m a little unclear as to what you mean. Winternitz (W-OTS) is a hash-based digital signature scheme. ChaCha is a stream cipher for symmetric encryption. Do yo

I’m a little unclear as to what you mean. Winternitz (W-OTS) is a hash-based digital signature scheme. ChaCha is a stream cipher for symmetric encryption. Do you mean a Winternitz signature digest encrypted with ChaCha, or are you proposing a ChaCha derivative hash function, like Blake? In either case, I don’t see what it gets you to use the post-quantum signatures anyway, then add the overhead of ChaCha.