Consider supporting SipHash

[dd86k]

A few pitched in the idea to support SipHash.

As interesting as SipHash is, it is not designed as a general-purpose hashing function, since its goal is to be used as a pseudorandom/MAC function:

As a secure pseudorandom function (a.k.a. keyed hash function), SipHash can also be used as a secure message authentication code (MAC). But SipHash is not a hash in the sense of general-purpose key-less hash function such as BLAKE3 or SHA-3. SipHash should therefore always be used with a secret key in order to be secure.

Meaning, even implementing this using a keyless-default approach renders the implementation and security pointless. Because ddh is supposed to be closest to sha512sum(1), openssl dgst, b3sum, and the like.

[dd86k]

One possibility could be, if siphash was implemented, to force the --key option to be used (or issue a warning on stderr?), which could make siphash an interesting feature then. Though, likely not one I'd use to verify file integrity for my downloads unless sites started to offer them. Maybe one day?