Reply to post: Re: Floating point crypto operations?

Intel chip flaw: Math unit may spill crypto secrets from apps to malware

Cynic_999 Silver badge

Re: Floating point crypto operations?


good for X^Y which is rather frequent in cryptography


Not that I know of.

AES, 3DES etc. uses table-lookups and logical operations (e.g. rotates, xor ), I can't think of any use for a conventional FPU in any symmetrical key encryption I've worked with.

Public/private key cryptography does use a form of exponential arithmetic - but on "bignumbers" which must be handled using a very different (and strange) form of modulo arithmetic that again, I cannot see a conventional FPU providing much assistance with apart from a slight boost computing partial products of bignumber multiplies and Montgomery inverses, which would not leave any useful scraps in the registers.

I've implemented several common encryption and hashing functions as well as public key encryption using assembler on both Z80 and ARM based processors. An FPU was of no significant help, but several ARM based chips contain a hardware encryption engine, one of which even does bignumber functions such as modulo exponential and Montgomery multiplication etc.

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