21,885 reputation
12991
bio website
location Paris, France
age
visits member for 3 years, 4 months
seen 10 hours ago

I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Nov
29
answered Does SHA-1 hash have quasi commutative property?
Nov
29
comment Cracking RSA with Small exponent 5
@codeomnitrix: If there is no quotes before and after password, then why is it that the "Known message bits" are precisely the ASCII encoding of Anonymous: This door has RSA encryption with exponent 5 and the password is: ', INCLUDING a final ' ?
Nov
28
comment Collision in Merkle–Damgård without a collision in compression function
Welcome to crypto.SE! $\;$ Is your claim that SHA-1 without insertion of the extra 1 bit is breakable? Are you exhibiting an explicit collision? If yes, what are the two colliding messages? $\;$ I'm trying to follow you, but fail. If guess you mean $f:\{0,1\}^{128+512+1}\to\{0,1\}^{128}$ (written $f:\{0,1\}^{128+512+1}\to\{0,1\}^{128}$ on this nice website, which handles a subset of $\TeX$), but then I'm getting lost; what's $y$, why does the binary representation of 24 matters (I get that $24=512-488$ but fail to see the significance), what is $z$, what is "z1=f 0^129||y1 z1" meaning?
Nov
28
revised secure embedded/microcontroller crypto using AES-ctr with hmac-sha2
dicsuss limits of diversified keys
Nov
28
revised secure embedded/microcontroller crypto using AES-ctr with hmac-sha2
Polish
Nov
28
comment Cracking RSA with Small exponent 5
My reading of the amended statement is that the plaintext is of the form: $m=2^{8(k+1)}a+2^{8}b+c$ with $a=$1779358514627318781383126548094807672538311874318159242622686075224638123273‌​733409785484042478408686091630450639923610751161891182321936751949320492657334925‌​6096527256865557690760788844583 the integer matching ASCII Anonymous: This door has RSA encryption with exponent 5 and the password is: ', $b$ the integer matching the ASCII password, $c=$39 matching ASCII ', and $k$ the number of characters in the password. $\;$ Can this be confirmed?
Nov
28
comment Cracking RSA with Small exponent 5
The question has changed considerably. I doubt that the ciphertext really follows and the password is: as in the fragment of the question below So the whole message is -. I conjecture that the password follows. Assuming that, this appears to be an exercise on Coppersmith's method. Suggestions: study section 4 in Dan Boneh's Twenty Years of Attacks on the RSA Cryptosystem; and express the plaintext as a linear function of the password. Or just brute-force the password.
Nov
28
revised secure embedded/microcontroller crypto using AES-ctr with hmac-sha2
Publishable version
Nov
28
answered secure embedded/microcontroller crypto using AES-ctr with hmac-sha2
Nov
27
comment Small Encryption Exponent
@codeomnitrix: I scratched my head and failed to see how Coppersmith's method (also here) could help in your other question as it originally stood; but the modified one is very different!
Nov
27
revised Maximum length in bits of the product n=pq
generalisation to product of odd primes
Nov
26
comment RSA OAEP: prevention of partial decryption of ciphertexts
Quick hint: contrast to the scheme attacked in this reference, and its reference 2.
Nov
26
revised Are there any digital signature algorithms in common use that result in 32-byte signatures?
remove repetiton, more explicit signature step 5
Nov
26
revised Are there any digital signature algorithms in common use that result in 32-byte signatures?
fix that M' was used without definition; explicit size overhead.
Nov
26
comment Minimum number of independent trials needed to detect a bias
That seems to be the correct order of magnitude. Statisticians have more precise evaluations, taking into account the confidence level that we want in the conclusions. We are talking about a Chi-squared test with one degree of freedom. There are also methods to decide dynamically if we can stop the test or continue, for given confidence levels or reaching the wrong conclusions.
Nov
26
comment Maximum length in bits of the product n=pq
@cryptoclk: the maximum size indeed is 2048 bits; the answer I commented reaches the correct numeric answer to the question, but puts that in a formally incorrect statement (notice total is not the same as maximum).
Nov
26
comment Maximum length in bits of the product n=pq
@pushpen.paul: NextPrime[2^1023]-2^1023 is 1555 according to WolframAlpha
Nov
26
revised Are there any digital signature algorithms in common use that result in 32-byte signatures?
Add missing term at verification step 6
Nov
26
revised Maximum length in bits of the product n=pq
Per request, explain how things are in practice.
Nov
26
revised Are there any digital signature algorithms in common use that result in 32-byte signatures?
Fix RSA public key fuction in verification