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In Android, Adiantum is an alternative to AES-XTS for devices without AES instructions.

I cannot understand the reason for why such a convoluted scheme was chosen.

There are 128-bit ARX block ciphers that could have been a drop-in with XTS infrastructure already in place.

Or using a BLAKE quarter round on 64-bit processors, a 256-bit block cipher.

DroidQ
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1 Answers1

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Because Adiantum is faster than ARX XTS ciphers. If you look at the performance comparison in timestamp 13:05 of this video, it shows Adiantum being faster than Speck in XTS mode, which is a lightweight ARX cipher itself. This is due to Adiantum using primitives such as ChaCha12, Poly1305, and NH which are very fast on software.

DerekKnowles
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