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Dec
6
comment SHA1 Collisions - what about practical attacks?
Great answer, really !!
Dec
5
comment SHA1 Collisions - what about practical attacks?
Thanks, such a great answer ! But "thus allowing forgery of a slightly different certificate beneficial to the attacker" , when it is about hash fonction, "slightly" difference in input doesn't mean "near output", so why is it an advantage to have chosen fields and "slightly" different ?
Dec
5
accepted SHA1 Collisions - what about practical attacks?
Dec
5
comment SHA1 - SSL/TLS Cipher Suite
@acid Thanks for your comment, but actually, padding could be used to resolve the "modulus size" problem, no ? As when you want to encipher large file with public key.
Dec
5
awarded  Commentator
Dec
5
comment SHA1 Collisions - what about practical attacks?
Ok password may not be the perfect exemple, in the case of digital certificates, the plain text has to be "understandable" because if not, the certificate would be refused by browser. That's the issue !!
Dec
4
revised SHA1 Collisions - what about practical attacks?
added 8 characters in body
Dec
4
asked SHA1 Collisions - what about practical attacks?
Dec
4
comment SHA1 - SSL/TLS Cipher Suite
@CodesInChaos Thanks for answering. I am know wondering why CA signs the certificate hash rather than the "raw content", there couldn't be collisions, I guess it is obvious, like performances when signing, perhaps also signature size, but x509 certificate are rather short file. Any idea ?
Dec
4
comment SHA1 - SSL/TLS Cipher Suite
@CodesInChaos In fact, an attacker wouldn't need to get the CA to sign the "fake" certificate, because if the two certificates have the same hash, they have the same signature (private key + hash). So the attacker can just get the signature of the "original" certificate (public info) and appends this signature on the fake one. No ?
Dec
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revised SHA1 - SSL/TLS Cipher Suite
I think you mean "still secure" and note "not secure"
Dec
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accepted SHA1 - SSL/TLS Cipher Suite
Dec
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comment SHA1 - SSL/TLS Cipher Suite
@CodesInChaos Ok I see, the "attack" is before CSR is made.
Dec
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revised SHA1 - SSL/TLS Cipher Suite
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Dec
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comment SHA1 - SSL/TLS Cipher Suite
Ok but i can't understand how attackers could forge SHA1 certificate signature, as the hash is still "protected" by the signature (CA private key). So forgin the hash with collisions, ok, but one would detect that hash is not trusted anymore (signature would'nt be the same). I miss something ?
Dec
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suggested approved edit on SHA1 - SSL/TLS Cipher Suite
Dec
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comment SHA1 - SSL/TLS Cipher Suite
@CodesInChaos Ok thanks, but what about cipher suites which use SHA1 as a signature scheme ? Will they be considered "deprecated" ?
Dec
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asked SHA1 - SSL/TLS Cipher Suite
Dec
1
awarded  Editor
Dec
1
revised Corporate PKI - SHA1 deprecation
added 82 characters in body