You wrote:
Now that the more ciphers in nettle work with fix key size, maybe it would be a good idea to drop the length argument also from the nettle_set_key_func typedef? This is used primarily for struct nettle_cipher (nettle-meta.h), where using a function pointer with more than one size makes little sense.
How would you then handle ciphers that accepts arbitrary key sizes?
Also, other AES-style algorithms, in particular, twofish and camellia, could have similar changes as AES. E.g., the twofish implementation appear to zero-pad keys of unusual sizes up to the next standard size. Is that an important feature, or can I change it to just have twofishN_setkey (struct twofishN_ctx *, const uint8_t *key), for n = 128, 192 and 256?
I'd say drop it unless someone has a use-case for it.
/Simon