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Sep
8
answered Efficiency of McEliece cryptography (ciphertext expansion)
Sep
4
comment Padding size with a CBC Block cipher in TLS
@chadianscot: no, you always have a padding length field. Otherwise, how would the decryptor know whether or not there is padding there?
Sep
3
reviewed No Action Needed Where is Signaturevalue in Certificate?
Sep
3
comment Do $v_1=\alpha\cdot r_1$ and $v_2=\alpha\cdot r_2$ leak information about $\alpha$
@user13676: I assume you meant "what if some of the $r_i$ values are smaller than $p/\alpha$. So what if that happens? How can the attacker get any information about whether that happens? As my answer stated, the values that the attacker sees is consistent with any nonzero $\alpha$. The attacker can guess that $r_i \cdot \alpha < p$, however without any way of validating that guess, that doesn't tell him anything.
Sep
3
answered Do $v_1=\alpha\cdot r_1$ and $v_2=\alpha\cdot r_2$ leak information about $\alpha$
Sep
3
answered TLS Cipher Suite definitions
Sep
2
revised qkd - Does BB84 rely on a prearranged code?
added 44 characters in body
Sep
2
comment What is the state of cryptographic obfuscation in 2015?
Actually, both examples can be fairly easily done using standard cryptography. For example, in the first case, we can have the program compute SHA512(input), if the first 32 bytes is a specific pattern, then the second 32 bytes xor'ed with a specific constant is the launch code.
Sep
2
answered qkd - Does BB84 rely on a prearranged code?
Sep
1
comment Using a hash (like SHA-256) vs AES as the source for pseudo-random values in Feistel network?
@SEJPM: no matter what primitive you use, you need to care about keys; a totally unkeyed FPE algorithm may have some security problems...
Aug
29
awarded  Nice Answer
Aug
28
comment Generate RSA-2048 private key for a VERY fast decryption (don't care if it will be unsecure)
@SEJPM: $d=1$ if for every prime factor $p$ of $n$, we have $e \equiv 1 \bmod p-1$. So, I picked an $e$ where $e−1$ is divisible by a lot of numbers, and then tested all those divisors to find which ones were one less than a prime, and then made sure that the product of all those primes was $>2^{2048}$
Aug
28
revised Generate RSA-2048 private key for a VERY fast decryption (don't care if it will be unsecure)
edited body
Aug
28
answered Generate RSA-2048 private key for a VERY fast decryption (don't care if it will be unsecure)
Aug
28
comment Calculating $\mathbb F_{p^2}$-rational points of an elliptic curve defined over $\mathbb F_p$
@111: In the field $GF(p^2)$, we often use a representation $ai + b$, where $i$ is one of the field elements with $i^2 = -1$ (and it turns out not to matter which, as they are isomorphic). In your representation, $i$ is one of two values $4z+3$ and $7z+8$.
Aug
28
awarded  Enlightened
Aug
28
awarded  Nice Answer
Aug
27
comment Does Curve25519 only provide 112 bit security?
@RichieFrame: actually, 4 of those bits are already accounted for by the fact that the full order size is 255 (not 256) bits, and that the cofactor is 8. DJB does leave one addition bit fixed (however, that's not inherent in the Curve25519; that's how Dan suggests it be used); however even with that change, that reduces the strength to 125.5 bits...
Aug
27
answered Does Curve25519 only provide 112 bit security?
Aug
27
comment What was the NSA's reasoning for making their bitwise combination functions in SHA-1 the way they did?
Well, one obvious distinction between their F1 and yours is that their F1 has evenly distributed output (assuming the inputs are evenly distributed); yours has a distinct bias towards 1 bits.