/* * X9.42 PRF * (C) 1999-2007 Jack Lloyd * * Distributed under the terms of the Botan license */ #include #include #include #include #include #include #include namespace Botan { namespace { /* * Encode an integer as an OCTET STRING */ MemoryVector encode_x942_int(u32bit n) { byte n_buf[4] = { 0 }; store_be(n, n_buf); return DER_Encoder().encode(n_buf, 4, OCTET_STRING).get_contents(); } } /* * X9.42 PRF */ SecureVector X942_PRF::derive(size_t key_len, const byte secret[], size_t secret_len, const byte salt[], size_t salt_len) const { SHA_160 hash; const OID kek_algo(key_wrap_oid); SecureVector key; u32bit counter = 1; while(key.size() != key_len && counter) { hash.update(secret, secret_len); hash.update( DER_Encoder().start_cons(SEQUENCE) .start_cons(SEQUENCE) .encode(kek_algo) .raw_bytes(encode_x942_int(counter)) .end_cons() .encode_if(salt_len != 0, DER_Encoder() .start_explicit(0) .encode(salt, salt_len, OCTET_STRING) .end_explicit() ) .start_explicit(2) .raw_bytes(encode_x942_int(static_cast(8 * key_len))) .end_explicit() .end_cons().get_contents() ); SecureVector digest = hash.final(); const size_t needed = std::min(digest.size(), key_len - key.size()); key += std::make_pair(&digest[0], needed); ++counter; } return key; } /* * X9.42 Constructor */ X942_PRF::X942_PRF(const std::string& oid) { if(OIDS::have_oid(oid)) key_wrap_oid = OIDS::lookup(oid).as_string(); else key_wrap_oid = oid; } }