Difference Between AES and Twofish

AES vs Twofish

The Advanced Encryption Standard, or AES, is currently the latest standard that has been adopted by United States government for encrypting top secret information. The label of AES was not initially meant for a single encryption method; instead it was a competition between many. Among the five finalists are Rijndael and Twofish. Rjindael won and was adopted as AES while Twofish obviously did not.

AES is a block cipher and uses a substitution-permutation network for encrypting the data. On the other hand, Twofish uses a Feistel network to accomplish the same task. This means that Twofish is very similar, albeit much more complex than the older standards DES (Data Encryption Standard) and 3DES (Triple DES). Despite being similar to the older DES encryption, Twofish is unbreakable; even in theoretical perspective. AES is also a very robust encryption standard especially with very long key lengths. There are instances though where AES encryption is breakable. It is not very alarming though as the break was done on the 8 rounds version, which is not in use. There is still no proven attack where data was actually gathered by breaking the AES encryption.

Depending on the length of the key, AES implements different number of round of encryption. For key sizes of 128 bits, 192 bits, and 256 bits, the number of rounds is 10, 12, and 14 respectively. Twofish does not vary the number of rounds for any key size. Instead, it uses a fixed number of 16, regardless.

Probably the primary reason why Rijndael was chosen for AES rather than Twofish is the fact that it is very efficient when it comes to hardware. It requires less memory and fewer cycles in order to encrypt data. Although the impact is smaller on high-end devices, for low end devices the gap can be very significant.

Although it might seem like breaking the cipher is the only way to break into a secure system. It is actually the most difficult way to do it; especially when you are facing a very tough encryption standard like both AES and Twofish are.

Summary:
1. AES is actually Rijndael while Twofish is one of the AES finalist
2. AES uses the substitution-permutation network while Twofish uses the Feistel network
3. AES is breakable in some forms while Twofish is
4. AES implements fewer rounds than Twofish
5. AES is more efficient than Twofish

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