des-ede-cbc密码的密钥长度是多少? [英] What is the Key Length of the des-ede-cbc cipher?
问题描述
我知道DES的密钥长度为56，但是ede是什么意思，它会影响密钥长度吗?
Openssl
des-ede-cbc
可以使用不少于3个密钥大小的三重DES，DES-EDE或TDEA.
最合乎逻辑的形式在每个阶段使用3个单独的密钥(加密，解密，然后再次加密，这是EDE的含义).它的密钥大小是56位或168位的3倍，但通常使用奇偶校验位(每个字节的最低有效位)进行编码，总共为192位.由于中间相遇攻击(在设计阶段已为人所知)，安全性只有112位左右，因此不要仅仅被密钥大小所迷惑.
两个密钥DES-EDE在加密阶段使用相同的密钥.因此，由于各种攻击，密钥大小为112位，编码为128位，安全性大约为80位.如今，80位可能还只是短边.
最后，单键DES-EDE主要用于向后兼容.第一次加密和解密会互相抵消，因此只剩下一个加密.您可以猜测密钥的大小；单键TDES从未在软件中使用过，也可能不受支持(仅在硬件中有意义，在硬件中，除了DES-EDE之外，您不希望提供DES的单独实现).
DES-EDE比良好的AES实现要慢得多，并且对于128位的密钥大小(使用非常复杂的攻击)，AES的安全性约为126,8.因此，如果有机会，请选择AES.
I know that DES has a key length of 56, but what does the ede mean and does it effect the key length?
Openssl
des-ede-cbc
Triple DES, DES-EDE or TDEA (formally speaking) can be used with no less than 3 key sizes.
The most logical form uses 3 separate keys for each of the phases (Encrypt, Decrypt and then Encrypt again, which is the meaning of EDE). It has a key size of 3 times 56 bits or 168 bits, but those are usually encoded with parity bits (the least significant bit of each byte), making 192 bits in total. Due to a meet-in-the-middle attack (already known at the design phase) the security is only around 112 bits, so don't be fooled by the key size alone.
The two key DES-EDE uses the same keys for the Encrypt phases. The key size is therefore 112 bits, encoded as 128 bits and a security of just around 80 bits, due to various attacks. 80 bits is probably just a bit on the short side nowadays.
Finally single key DES-EDE is mainly used for backwards compatibility. The first encrypt and decrypt cancel each other out so you're left with just one encrypt. You can guess the key sizes; single key TDES is never used in software and may not be supported (it just makes sense in hardware, where you don't want to supply a separate implementation of DES in addition to DES-EDE).
DES-EDE is much slower than a good implementation of AES, and AES has a security of around 126,8 for a key size of 128 bits (using a very complicated attack). So if you have any chance, choose AES instead.
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