Timeline for What was the NSA's reasoning for making their bitwise combination functions in SHA-1 the way they did?
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
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| Aug 30, 2015 at 20:40 | vote | accept | BonBon | ||
| Aug 27, 2015 at 19:52 | comment | added | user13741 | These functions were also used in MD4 and MD5, which predate SHA-1. So I guess the best person to ask would be Ron Rivest. I think one of the biggest factors was performance. The F1 function above can be evaluated by a single "select bits" instruction on processors that have one, as F1 can be interpreted as "if B then C else D". | |
| Aug 27, 2015 at 12:41 | answer | added | otus | timeline score: 12 | |
| Aug 27, 2015 at 8:07 | history | tweeted | twitter.com/#!/StackCrypto/status/636812250678960128 | ||
| Aug 27, 2015 at 6:42 | history | edited | otus | CC BY-SA 3.0 |
edited tags; edited title
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| Aug 27, 2015 at 4:02 | comment | added | BonBon | I just used that as an example, but thanks for your reply. | |
| Aug 27, 2015 at 3:28 | comment | added | poncho | Well, one obvious distinction between their F1 and yours is that their F1 has evenly distributed output (assuming the inputs are evenly distributed); yours has a distinct bias towards 1 bits. | |
| Aug 27, 2015 at 1:35 | comment | added | BonBon | As a plus, if you have source for this reasoning, that would be greatly appreciated. Thanks! | |
| Aug 27, 2015 at 1:33 | review | First posts | |||
| Aug 27, 2015 at 2:38 | |||||
| Aug 27, 2015 at 1:31 | history | asked | BonBon | CC BY-SA 3.0 |