Which is stronger, IDEA, CAST, 3DES or Twofish?
This is a contentious and subjective issue. None of these algorithms has either been broken or had any serious doubts cast upon their strength. Some people don’t trust 3DES because it is based upon DES, which is produced by the NSA. However, respected cryptographers hold 3DES in very high regard. CAST5, as implemented in PGP, has not been subjected to any successful analysis, but Bruce Schneier has said the following [Sch98a] “I give a big yuk to CAST-128” and [Sch98c] “I don’t buy the design process.”. Twofish is far to new to be considered stronger than either of the other 3 ciphers. In time it may be seen as secure, but for now it just hasn’t been subjected to enough analysis. Some have claimed that because Blowfish is trusted, we should trust Twofish [Blu98] though this is simply not true. They are both BFN etc and the key schedule consists of iterations of a function used in encryption, but there are also many differences between the two ciphers. Small changes in block ciphers can
