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


Apr
12
answered Why are collision attacks important when talking about MAC schemes?
Apr
12
comment Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$?
Would someone care to compose an answer, preferably in zero knowledge for dummies style so that I can catch on?
Apr
12
revised Is there a simple zero knowledge proof of $x$ for $b=x^x\pmod p$?
TeXify the title
Apr
12
revised Turning a cipher into a hashing function
deleted 24 characters in body
Apr
12
revised Turning a cipher into a hashing function
Polish
Apr
12
revised Turning a cipher into a hashing function
edited body
Apr
12
revised Turning a cipher into a hashing function
Describe the Hirose construction
Apr
11
answered Turning a cipher into a hashing function
Apr
11
comment Could RDRAND (Intel) compromise entropy?
Great and very relevant reference!
Apr
11
comment What is the asymptotic complexity of RSA and paillier cryptosystem algorithm?
Welcome to crypto.SE! Some suggestions: A) Do a minimum of research on your own, and summarize your findings in the question. If you stump on something, state what, likely you'll get explanation. B) Confirm you want the time complexity on a fixed-word-size computer. C) Determine if you want the asymptotic complexity for a multiplication algorithm used in cryptographic practice, or a theoretical one; that changes the answer, a lot. D) Ponder the typographical consequence of the etymology of the second cryptosystem in the question.
Apr
11
comment How we transfer 128bits cipher to a 4x4 matrix for AES input?
A 4x4 matrix has 16 entries. Each entry is 8 bits. 16 times 8 bits is 128 bits. Anything unclear?
Apr
10
comment Security of this deterministic encryption scheme
"The same key for confidentiality and integrity" is bad in principle, but since integrity is with HMAC-SHA256, and confidentiality with CBC, I see no theoretical attack possible. "There is no MAC on the ciphertext", but as long as as the alleged plaintext is discarded when the MAC does not check, I do not see a theoretical issue. On a practical standpoint, the decryption is directly exposed to side-channel attacks (DPA..), and if the encryption key leaks due to that, integrity also goes down the drain. Of course indentical plaintext leads to identical ciphertext.
Apr
10
revised Rotation table for 8 round DES
Cautionary note
Apr
10
revised Rotation table for 8 round DES
Handle question update
Apr
10
comment Why are Fortuna entropy pools reset after a reseed?
Discounting the counter, the master state evolves per $K←\text{SHA}_d\text{-256}(K||s)$ where $s$ is built from the pool outputs. That makes it computationally impossible to calculate the past contents of master state from current contents of master state and pools, even if that fully revealed past pool outputs. However, indeed, a reset of a pool after use makes it harder to verify a guess of the past contents of the master state from current contents of master state and pools.
Apr
9
revised Why are Fortuna entropy pools reset after a reseed?
Fortuna's master state is not huge, it is sufficient.
Apr
9
revised Rotation table for 8 round DES
Polish
Apr
9
revised What is h in the improved solution of RSA algorithm?
Add PS
Apr
9
answered What is h in the improved solution of RSA algorithm?
Apr
9
revised Rotation table for 8 round DES
Improved sugestion.