RSA也可以用来为一个消息署名。假如甲想给乙传递一个署名的消息的话，那么她可以为她的消息计算一个散列值，然后用她的密钥加密这个散列值并将这个“署名”加在消息的后面。这个消息只有用她的公钥才能被解密。乙获得这个消息后可以用甲的公钥解密这个散列值，然后将这个数据与他自己为这个消息计算的散列值相比较。假如两者相符的话，那么他就可以知道发信人持有甲的密钥，以及这个消息在传播路径上没有被篡改过。-RSA can also be used as a signed message. If i want to give B send a signed message, then she can for her calculation of a message hash value, and then use her key encryption of the hash value and the " signed"　the message added to the back. This message is only used her public key can be decrypted. B received the news with a public key can decrypt the hash value, then this data with his own message for the hash value calculated in comparison. If the two match, then the sender to know him a key holder, as well as in the dissemination of this message on the path had not been tampered with.