rfc3961_derive_checksum_key
int rfc3961_derive_checksum_key(const struct krb5_enctype *krb5,
.derive_checksum_key = rfc3961_derive_checksum_key,
.derive_checksum_key = rfc3961_derive_checksum_key,
.derive_checksum_key = rfc3961_derive_checksum_key,