Why is Scrypt default work factor not a power of 2?

[v3rm0n]

Looks like it is 18 in the reference implementation, but some Scrypt implementations strictly check for it to be a power of 2 and will fail if it isn't so. Like https://github.com/bcgit/pc-dart/blob/master/lib/key_derivators/scrypt.dart#L50 for example.

Just wondering because this is causing issues for me if I'm trying to decrypt something in Dart implementation when it is encrypted with reference implementation.

[FiloSottile]

The number in the age recipient is the log2 of the work factor, indeed because only powers of two are valid parameters. Some implementations just take 18 instead of 2^18 so they can save space and avoid checking that the value is a power of two. Looks like Dart doesn’t, so you’ll have to pass in 2^n where n is the value in the header. Sent from a small keyboard

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On May 18, 2022, at 23:00, Maido ***@***.***> wrote:  Looks like it is 18 in the reference implementation, but some Scrypt implementations strictly check for it to be a power of 2 and will fail if it isn't so. Like https://github.com/bcgit/pc-dart/blob/master/lib/key_derivators/scrypt.dart#L50 for example. Just wondering because this is causing issues for me if I'm trying to decrypt something in Dart implementation when it is encrypted with reference implementation. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.

[v3rm0n]

Thanks!