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| bio | website | |
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| visits | member for | 7 months |
| seen | yesterday | |
| stats | profile views | 4 |
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Apr 29 |
comment |
Custom crypto library in C I don't understand how the sleep function can help you prevent timing attacks : how do you know how much time you need to sleep ? Also if your using the worst case running time as a reference you need to know what it is precisely on the platform your library is running which requires fine tuning after every install which. May I ask why you're not using and existing library (NaCl, openssl ect) ? |
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Apr 10 |
answered | EC equivalent for RSA-OAEP |
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Apr 9 |
answered | Signature schemes for underpowered devices (8bit microcontroller) |
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Mar 14 |
revised |
Is this encryption algorithm build from MD5 secure? added reference to Hash CFB |
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Mar 6 |
comment |
Is this encryption algorithm build from MD5 secure? Look at the effect of flipping a bit in the last ciphertext block, if I understood the algorithm correctly this only flips the corresponding bit in the last plaintext block which might be useful if you know the format of the message even if you don't know the content |
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Mar 6 |
answered | Is this encryption algorithm build from MD5 secure? |
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Feb 23 |
comment |
Why nobody considers counter re-keying as a standard Block Cipher Mode? Interestingly those approaches are looked at carefully in the context of side channel attacks : this prevents differential power analysis (since we cannot get traces on the same key) and the counter measures for SPA are well understood |
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Feb 19 |
answered | Could use an explanation of the notation for an oracle adversary |
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Feb 15 |
comment |
Encrypting a key with the same key Practically speaking it's so unlikely that it cannot be called "insecure". Theoritically speaking, if you take a look at the insides of aes you'll see that the first operation is xoring the plaintext with the key, effectively cancelling the state whatever the key. From then on the only difference between $AES_K(K)$ and $AES_{K'}(K')$ will come from the difference in the key scheduling of both keys. Hope it helps |
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Feb 9 |
comment |
Name for identical operations for encryption and decryption What you consider a weakness can also become a strenght in some contexts. For example, embedded designs have very strict space requirements : having a encryption algorithm that is its own inverse is then something really valuable. Even in software it can be thought of as a good idea : less code means easier maintainability. Anyways I would say that while you're not wrong, if you can avoid it, do not give an encryption oracle to your adversary in the first place ! |
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Jan 24 |
comment |
Super-symmetric Stream cipher It means that if done well you have to independant stream ciphers |
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Jan 23 |
comment |
Initialize a PRNG with a password I think I understand but generating with weak randomness isn't worth the fact that you don't have to store your keys. If I could store 256 bytes I rather seed my DPRNG with actual randomness then use [tools.ietf.org/html/rfc2898#section-6.2] to protect the key ? |
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Dec 19 |
comment |
AES vs Blowfish taking key-length into account When considering the margin of security one should not forget that AES is THE target for more than 10 years now while the cryptanalitic effort on blowfish is not as strong nowadays |
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Dec 18 |
comment |
Good enough deterministic PRNG based on hashes Good point, I forgot about the key reduction step |
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Dec 17 |
comment |
Good enough deterministic PRNG based on hashes "In particular if the seed is longer than 128 bytes it becomes totally insecure" why ? |
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Dec 13 |
comment |
Probability that an attacker wins the discrete logarithm game when exponents are drawn from a subset There's even a tradeoff between the running time of your algorithm and the success probability since instead of failing if the input doesn't fall in the acceptable subset you can randomize your input via a multiplication by $g^r$ (with random $r$) and run it again. I think that's called Random Self Reducibility |
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Dec 7 |
comment |
RSA 4096 bit key benchmark I guess it's just vocabulary here but rather than ECDH an elliptic curve alternative for mary would be ECIES which uses ECDH as a key establishment scheme |
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Dec 7 |
comment |
using Post-quantum asymmetric ciphers instead of RSA @CodeInChaos what construction were you thinking about ? I don't think composition is a terrible idea but there are exemples in which it breaks. Maybe pick $r$ at random then $m_0\gets r\oplus m$ and $m_1 \gets r$ ? |
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Dec 7 |
comment |
Why are protocols often proven secure under the random oracle model instead of a hash assumption? Interestingly enough while a construction $H^2:x\to H(H(x))$ does not have this length extension property it is still distinguishable from a RO H^2 & HMAC |
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Dec 7 |
answered | RSA 4096 bit key benchmark |
