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A comment on Maybe Skip SHA-3. Parent comment

Re:Maybe Skip SHA-3 by cperciva on Thursday June 01, 2017 @01:29AM (#14458199)
If length extension attacks are a problem, you're using a hash function for something which a hash function is not intended to be used for; you probably wanted a MAC instead.
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Re:Maybe Skip SHA-3 by baby on Thursday June 01, 2017 @04:46AM (#14458821)
1. Yes. And people do that. I'm nkt talking about me. I'm talking about things I see in my work (I'm a consultant).

2. People should be able to do that. If you're expecting your hash function to behave somehow like a random oracle there is no reason that h(key|data) doesn't work. I see people using sha-2 to derive keys all the time. Even this is unsafe depending on how you do it.

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Re:Maybe Skip SHA-3 by 15155 on Thursday June 01, 2017 @02:47AM (#14458437)
Why must MAC mean "HMAC RFC2104?"
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Re:Maybe Skip SHA-3 by cperciva on Thursday June 01, 2017 @02:53AM (#14458459)
It doesn't. I said MAC, not HMAC.
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