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


Apr
7
answered XOR with constant key in CBC mode
Apr
7
revised XOR with constant key in CBC mode
Cleanup, rename, retag
Apr
7
revised RSA: Letting $p$ and $q$ have different bit-size
Last polish!
Apr
7
revised RSA: Letting $p$ and $q$ have different bit-size
Final polish
Apr
7
revised RSA: Letting $p$ and $q$ have different bit-size
Final polish
Apr
7
revised RSA: Letting $p$ and $q$ have different bit-size
Polish
Apr
7
revised RSA: Letting $p$ and $q$ have different bit-size
Polish
Apr
7
answered RSA: Letting $p$ and $q$ have different bit-size
Apr
6
awarded  Convention
Apr
5
comment Definition of a Statistical Test
Your understanding of what the formula means seems right to me. This test is designed with much more than 100 bits in mind, and I would say aims at having an extremely low false-positive rate.
Apr
4
comment Is that possible to use encryption higher than 256-bit?
These 128-bit and 256-bit are symmetric key sizes. Against brute force attacks: assuming computing ability doubles each year, we gain 1 extra year of security per bit; that used to be about right in the last 20 years of the 20th century, and is now more like 2 years per bit, and growing; 80 bits was very safe in 1990, and remains hard to crack nowadays (there's no public claim that it was attempted, much less done); 128 bits seems very safe for two decades; we can expect 256 bits will never be cracked by humanity because progress will slow or/and humanity vanish; so why care for 512 bits?
Apr
3
revised Cryptographic system with double keys with reversible order
fix location in reference article
Apr
3
revised Cryptographic system with double keys with reversible order
State the conjectured security of the Pohlig-Hellman Exponentiation Cipher
Apr
3
revised Cryptographic system with double keys with reversible order
Expand proof, make notation more consistent
Apr
2
comment Cryptographic system with double keys with reversible order
@tylo: Your remark is correct for the IND-CPA game played for public-key encryption, where encryption of chosen plaintext is always possible, and unstated. But for symmetric encryption, the textbook IND-CPA game allows the adversary to obtain a ciphertext for chosen plaintext before the challenge phase (at the price, in the deterministic encryption game, of not choosing it later on). I expanded my sketch to a full proof. Initially it was for deterministic encryption, but with minor tweaks it seems I have now proven that no symmetric scheme (including probabilistic) can provide commutativity!
Apr
2
revised Cryptographic system with double keys with reversible order
Remark for probabilistic cipher
Apr
2
revised Cryptographic system with double keys with reversible order
Change references to the IND-CPA game to a most accepted one
Apr
2
revised Cryptographic system with double keys with reversible order
Polish
Apr
2
revised Cryptographic system with double keys with reversible order
Back to "commutativity is incompatible with security under CPA".
Apr
2
revised Cryptographic system with double keys with reversible order
It may be that even a probabilistic encryption scheme can't be both commutative and IND-CPA secure