For example, if I use AES-CTR and use key of 44 bytes.
Will it be breakable or not and why?
How to use AES-CTR correctly?

  • 1
    $\begingroup$ The encryption function won't accept and won't use the additional bytes. You should use a vetted encryption library. $\endgroup$
    – Natanael
    Jan 22, 2020 at 19:02
  • 1
    $\begingroup$ Be warned that there are plenty of libraries out there that either add zeros or remove values from a key if the key size doesn't fit. PHP's mcrypt wrapper is a well known library that messes up keys like that. Other libraries use a PBKDF of some sorts if your key size is too large. Some libraries simply ignore it altogether, e.g. in C you generally don't supply a key size with the key at all, as AES-128 in itself already communicates the key size. All those libraries are bad implementations, if the key size is other than 16, 24 or 32 bytes then the library should stop with an error. $\endgroup$
    – Maarten Bodewes
    Jan 22, 2020 at 21:38


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