[Cryptography-dev] Is SHA-1 secure when used in HMAC and PBKDF2?

[Alex Gaynor]

It's also worth noting that the correct time to switch is not when
something is broken, it's well before then.

Alex

On Wed, Mar 15, 2017 at 5:14 PM, Paul Kehrer <paul.l.kehrer at gmail.com>
wrote:

> Echoing Alex's comments, SHA1's problems do not affect HMAC constructions
> so there's no current security issue. That said, optics in cryptography can
> be important (as you're seeing with your user requests now). You will save
> yourself a great deal of low grade noise in the future by simply switching
> now.
>
> On March 15, 2017 at 1:53:24 PM, Alex Gaynor (alex.gaynor at gmail.com)
> wrote:
>
> Hi David,
>
> You're correct that HMAC's security is still fine when used with SHA-1,
> HMAC-MD5 is even secure believe it or not.
>
> That said, I'd generally recommend people migrate to HMAC-SHA-256
>  anyways, to make analyzing their software easier.
>
> Alex
>
> On Wed, Mar 15, 2017 at 1:48 PM, David Lord <davidism at gmail.com> wrote:
>
>> Hello cryptography,
>>
>> Over at the Flask repos, we've had a number of requests to use SHA-256
>> instead of SHA-1 in a couple places.
>> Werkzeug defaults to SHA-1 as part of PBKDF2 to generate password hashes.
>> ItsDangerous defaults to SHA-1 as part of HMAC signatures.
>>
>> After some discussion I concluded that as used in those two methods,
>> SHA-1's collision issues were not relevant.
>> However, I'd like to get a second opinion from the cryptography experts.
>>
>> I can change the default to SHA-256, but if it's not actually making
>> things more secure then that's just increasing time and space for no reason.
>>
>> Thanks,
>> David
>>
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>>
>
>
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>


-- 
"I disapprove of what you say, but I will defend to the death your right to
say it." -- Evelyn Beatrice Hall (summarizing Voltaire)
"The people's good is the highest law." -- Cicero
GPG Key fingerprint: D1B3 ADC0 E023 8CA6
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