MD5Digest
MD5Digest((unsigned char*)timestamp.String(), md5sum);
void MD5Digest(unsigned char* in, char* out);
MD5Digest(hex_digest, (unsigned char*)a1.String(), a1.Length());
MD5Digest(hex_digest2, (unsigned char*)a2.String(), a2.Length());
MD5Digest(hex_digest, (unsigned char*)kd.String(), kd.Length());