Preventing Timing Attacks on String Comparison with Double HMAC Strategy (2015)

Posted by rdpintqogeogsaa on Sunday November 21, 2021 @03:35AM
from the paragonie.com dept.

https://paragonie.com/blog/2015/11/preventing-timing-attacks-on-string-comparison-with-double-hmac-strategy

( 7 comments | 35 points | on HN )

Re:Preventing Timing Attacks on String Comparison with Doubl... by ianopolous on Sunday November 21, 2021 @11:21AM (#29297371)

Neat idea! Especially on jitted platforms where the jit is likely to introduce a timing side channel.

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Re:Preventing Timing Attacks on String Comparison with Doubl... by rurban on Sunday November 21, 2021 @01:46PM (#29298636)

Using the timingsafe_memcmp C function would be faster and safer.

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Re:Preventing Timing Attacks on String Comparison with Doubl... by tatersolid on Tuesday November 23, 2021 @05:21AM (#29316262)

Not using C at all would be safer

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Re:Preventing Timing Attacks on String Comparison with Doubl... by iudqnolq on Sunday November 21, 2021 @03:41PM (#29299496)

As TFA says

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Re:Preventing Timing Attacks on String Comparison with Doubl... by dorianmariefr on Sunday November 21, 2021 @09:54AM (#29296539)

so hash(input) == hash(secret) ?

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Re:Preventing Timing Attacks on String Comparison with Doubl... by pornel on Sunday November 21, 2021 @02:01PM (#29298748)

No, `hash(hash(input)) == hash(hash(secret))`.

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Re:Preventing Timing Attacks on String Comparison with Doubl... by justinsteven on Sunday November 21, 2021 @06:06PM (#29300691)

No, `hmac(key=key, message=input) == hmac(key=key, message=secret)` where key is either a static secret key for comparison purposes, or random for each comparison.

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