Timeline for How strong if I combine two hash functions, such as MD5(SHA256(input))?
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| Nov 20, 2021 at 12:40 | review | Close votes | |||
| Dec 6, 2021 at 3:01 | |||||
| Nov 20, 2021 at 0:28 | comment | added | dave_thompson_085 | Aside from the fact storing truncated SHA256 is as good cryptographically, if you want you can store full SHA256 and have MySQL index only a prefix of it; see the manual. But that's not cryptography and is offtopic. | |
| Nov 19, 2021 at 20:04 | comment | added | kelalaka | What is the total data size? Why the collision is important for you? Why can't you use PRP that guarantees uniqueness provided that the data are unique? Your target is not clear to provide a full answer... And the B+ tree part is off-topic here. | |
| Nov 19, 2021 at 20:00 | comment | added | kelalaka | RIPEMD is better to be used than MD5, which Bitcoin already uses RIPEMD-160 | |
| Nov 19, 2021 at 18:27 | answer | added | fgrieu♦ | timeline score: 3 | |
| Nov 19, 2021 at 17:53 | history | reopened |
AleksanderCH fgrieu♦ |
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| Nov 19, 2021 at 17:40 | comment | added | fgrieu♦ | A SHA-256 (resp. MD5) hash is not of length 64 (resp. 32) when base-64 encoded. Using binary as search key has no good IT reason to be an issue, and has reasons to be faster. Since security goals of the overall system are not stated, we can't tell if they are met. I reopened the Q, but really: why would this be considered, with the broken MD5? Why not a modern truncated hash? | |
| Nov 19, 2021 at 16:07 | history | edited | Neil Niu | CC BY-SA 4.0 |
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| S Nov 19, 2021 at 15:56 | review | Reopen votes | |||
| Nov 19, 2021 at 17:57 | |||||
| S Nov 19, 2021 at 15:56 | history | edited | Neil Niu | CC BY-SA 4.0 |
added 523 characters in body
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| Nov 18, 2021 at 17:21 | comment | added | user491880 | Think about some other hash function much worse at collisions than MD5 -- say Hash(X) = 1... what would the security of Hash(SHA256(X)) be? The same logic applies to this question. | |
| Nov 18, 2021 at 15:37 | history | closed | Maarten Bodewes♦ | Not suitable for this site | |
| S Nov 18, 2021 at 15:27 | review | First questions | |||
| Nov 18, 2021 at 15:42 | |||||
| S Nov 18, 2021 at 15:27 | history | asked | Neil Niu | CC BY-SA 4.0 |