public-key-encryption - 在 Diffie-Hellman 中，中间进攻的人是如何工作的？

Question

在 Diffie-Hellman key 交换期间，我对中间人攻击的机制有疑问。我听说它可能发生在 key 协议(protocol)通信期间。但是在 CA(证书颁发机构)存在的情况下，接收者可以在接收到发送者的公钥时对发送者进行身份验证。因此，中间人如何攻击？

Answer 1

我认为您将基本的 Diffe-Hellman(一种 key 交换协议(protocol))与使用证书颁发机构(CA)的“认证版本”混淆了。

很好地解释了基本的 Diffe-Hellman 如何容易受到中间人的攻击 from RSA Labs .

"The Diffie-Hellman key exchange is vulnerable to a man-in-the-middle attack. In this attack, an opponent Carol intercepts Alice's public value and sends her own public value to Bob. When Bob transmits his public value, Carol substitutes it with her own and sends it to Alice. Carol and Alice thus agree on one shared key and Carol and Bob agree on another shared key. After this exchange, Carol simply decrypts any messages sent out by Alice or Bob, and then reads and possibly modifies them before re-encrypting with the appropriate key and transmitting them to the other party. This vulnerability is present because Diffie-Hellman key exchange does not authenticate the participants. Possible solutions include the use of digital signatures and other protocol variants."

然后是经过验证的版本，也称为 Station-to-Station protocol :

"Roughly speaking, the basic idea is as follows. Prior to execution of the protocol, the two parties Alice and Bob each obtain a public/private key pair and a certificate for the public key. During the protocol, Alice computes a signature on certain messages, covering the public value g^a mod p. Bob proceeds in a similar way. Even though Carol is still able to intercept messages between Alice and Bob, she cannot forge signatures without Alice's private key and Bob's private key. Hence, the enhanced protocol defeats the man-in-the-middle attack."

所以基本版本容易受到中间人攻击，而使用公钥证书的认证版本则不会。