29,193 reputation
453109
bio website bolet.org/~pornin
location Quebec City, Canada
age 38
visits member for 2 years, 9 months
seen 3 hours ago

Cryptographer, programmer in several languages (C, Java, several assemblies, Pascal, Forth...). I also have a life.


Dec
22
answered With Encrypt-then-MAC, and flexible protocols, do I need to authenticate the authentication?
Dec
21
awarded  Nice Answer
Dec
21
answered Can we say that if $P=NP$ there is no CPA secure public key encryption?
Dec
21
answered Solve a Modular Exponentiation
Dec
20
revised Should I use ECB or CBC encryption mode for my block cipher?
added 6 characters in body
Dec
20
answered Guessing encryption algorithm based on key and ciphertext
Dec
18
comment What is the difference between CSPRNG and PRNG?
Initial seed for a CSPRNG must come from something "which the attacker cannot know". Usually, this is "true randomness" extracted from hardware event. Typically, the system takes the time (down to the nanosecond, using the CPU cycle counter) at which hardware interrupts occurs, concatenates all these time values, and hashes the lot. Something similar occurs in the CSPRNG provided by usual operating systems (/dev/urandom on Linux, CryptGenRandom() on Windows...).
Dec
18
answered What is the difference between CSPRNG and PRNG?
Dec
18
awarded  Nice Answer
Dec
18
comment Multi-party encryption algorithm
Well, you do not need to renew the group key if someone merely exits. You need to renew the group key only when you want a former group member to become unable to read subsequent messages -- i.e. not really when someone decides to get some sleep; you renew the key when you want to evict a group member. This should be as frequent as banning/kicking participants (i.e. quite rare).
Dec
18
answered What is the best (thoroughly covering) textbook for application of LFSRs in cryptography?
Dec
18
answered Multi-party encryption algorithm
Dec
17
answered Diffie-Hellman insecure on addition modulo $n$
Dec
17
answered Calculation of time to crack SHA-256 hash
Dec
17
answered Why can an RSA signature be authenticated ONLY with the signer's public key?
Dec
16
comment Advantages of bilinear map
Yes, that's it: no known way with currently known pairings and curve types.
Dec
16
comment Advantages of bilinear map
Note that depending on what you want out of the pairing, you cannot necessarily use just any kind of curve. $G_1$ and $G_2$ of size $p$ prime, a computable one-way isomorphism from $G_1$ to $G_2$, easy hashing into $G_2$: you cannot have all three characteristics simultaneously.
Dec
16
answered Advantages of bilinear map
Dec
9
awarded  Enlightened
Dec
9
awarded  Nice Answer