Triple DES Overview

We have implemented the basic DES algorithm before, but we all know that the security of DES is not very high. The reason for this is that it has to come down to its key bit, which is to split the eight-bit check bit, the remaining 56-bit key is too short to be deciphered quickly at the current speed of normal machine operation. (This is what I see in my opinion. I have no practice)

For the above reasons, it is necessary to modify des, so there are multiple des. The so-called multi-Des is a repeated encryption operation through multiple keys, but its purpose is to increase the amount of keys. How many times does it make sense? I don't know. If you know, tell me/(^ o ^ )/~. However, the most widely used is the Triple DES encryption.

There are four different methods for Triple DES encryption:
1. DES-EEE3 mode. Three different keys (K1, K2, K3) are used and the three-step encryption algorithm is used.
2. DES-EDE3 mode. Use three different keys (K1, K2, K3) and encryption-decryption-encryption algorithm.
3. DES-EEE2 mode. Two different keys (k1 = K3, K2) are used and the three-step encryption algorithm is used.
4. DES-EDE2 mode. Use two different keys (k1 = K3, K2) and the encryption-decryption-encryption algorithm.

In usage mode, the total length of the first two keys is 168 bits, and the total length of the last two keys is 112 bits. From the attacker's point of view, the complexity of the former attack increased from O (2 ^ 56) to O (2 ^ 168), and the complexity of the latter two attacks increased from O (2 ^ 56) to O (2 ^ 112), which effectively overcomes the brute force attack of DES, according to the data, it has also enhanced the ability to defend against Difference Analysis and linear analysis (I am not familiar with this because I have not yet understood the principles of Difference Analysis and linear analysis ).

The above four modes have their own advantages. However, in the current feasibility analysis, the increase in attack complexity means that you need to increase the complexity of computing during encryption, therefore, we need to find a balance between efficiency and security.