k_pad
u8 k_pad[SHA1_BLOCK_SIZE];
prepare_kipad(sha.k_pad, key, key_sz);
crypto_shash_update(shash, sha.k_pad, block_size);
prepare_kopad(sha.k_pad, key, key_sz);
crypto_shash_update(shash, sha.k_pad, block_size);
k_self, k_fn, k_spec, k_pad,\