Which cascade in VeraCrypt is the safest? (assuming same password, keyfile strength etc) a] Serpent(Twofish(AES)) b] AES(Twofish(Serpent)

What could the difference be? I can't think of any and I don't uderstand why there are 2 options. Which one would you choose and why?

Both options for the 3-cipher cascade are equally safe.

All three algorithms are strong with no known issues. Veracrypt uses them in well-studied modes that also have no known issues.

If you were worried about one of the algorithm implementations being vulnerable to some sort of side channel attack, then I would use that one as the last to be applied. But in the context of most Veracrypt usage, someone who can mount a side channel attack, will probably just install a keystroke logger and steal the password directly.

So bottom line: There is no real difference, and you can arbitrarily choose one with no real impact.

You also ask for an opinion about what the community would choose, so I'll offer mine: The real threat is bad passwords or implementation bugs not weak algorithms, so I'd go with the highest performance single-pass algorithm. A three cascaded cipher implementation is overkill.

We should take into consideration the results of the cryptanalysis done by NIST and the results were:

Rijndael(AES) 86-10 = 76
Serpent 59-7   = 52
Twofish 31-21 = 10
RC6 23-37 = -14
MARS 13-83 = -70


Therefore, I would rather use AES first (the outermost encryption layer should be the hardest to break). Also it fits to mention than since AES became standard there were lots of research done trying to break the code and at this moment no practical way to break neither weaken AES has been possible. The rest of algorithms haven't been researched that much.

Truecrypt is an very popular encryption tool that also uses a cascade of encryption algorithm. This could be a good option since this tool has been considered a very effective encryption tool in previous years. The cascade they use is: AES-Twofish-Serpent with the XTS method.

• VeraCrypt is a free disk encryption software by IDRIX (idrix.fr) and it is based on TrueCrypt 7.1a. – abraza Aug 22 '17 at 18:33
• The sentence Therefore, I would rather use AES first (the outermost encryption layer should be the hardest to break) is contradictory. The encryption used first would be the innermost layer. Which do you mean? – mat Aug 22 '17 at 20:25