Cryptography Weekly Newsletter

Cryptography newsletter

Top new questions this week:

The REACT transform and Replayable CCA

Before stating my questions, let us recall the REACT transform [OP01], which enables to construct a CCA-secure hybrid PKE scheme, $\varepsilon'_{pk}$, from an OW-CPA PKE scheme …

malleability ind-cca  
asked by cygnusv 6 votes
answered by Travis Mayberry 3 votes

Elliptic Curve Cryptography

I have been trying this for a while. But I couldn't get it. How can I determine the point of intersection of the tangent line at (0, 0) on the curve $y^2 + y = x^3 + x^2$ ?

elliptic-curves  
asked by Kiran 5 votes
answered by albgarse 6 votes

OTT service using FPE

Would it be possible to create an Over-The-Top communication utility that will encrypt voice using format preserving encryption (voice clear-text to audio encrypted stream) and send that over an …

protocol-design compression format-preserving  
asked by user1028028 4 votes
answered by otus 3 votes

Is it secure to use Diffie-Hellman key agreement to generate a nonce?

I have a system, using AES, in one of the modes that uses a nonce and authentication. We have a pre-shared key, and to agree about initial nonce we could use Diffie-Hellman, using the resulting …

aes diffie-hellman initialization-vector  
asked by Yoav R. 4 votes
answered by otus 1 vote

Key Derivation from random salted seed, HMAC and HMAC based KDF

I would like to generate a key which would be good enough to be used for encryption with AES in a mobile environment. My idea is to use as a seed ''random attributes'' from a mobile device. Is hashing …

hmac salt kdf kbkdf  
asked by Hashed 4 votes
answered by owlstead 1 vote

Implementing CD serial key system

I am trying to create a system where to unlock the application one needs to enter a serial code. I have read many articles on the theme but there are two problems bugging me. One is, If I have a …

elliptic-curves signature protocol-design authentication  
asked by user2332868 4 votes
answered by otus 3 votes

Compression function to guarantee randomness of one time pads?

First of all, I would like to note that I am not building my own crypto. I am simply curious and would like to learn. What I am wondering is this: if we are worried about randomness of something …

hash one-time-pad compression  
asked by Bobby Newmark 4 votes
answered by owlstead 4 votes

Greatest hits from previous weeks:

No SHA-1 Collision? Yet SHA1 is broken?

Is there a known pair of distinct bit strings (A,B) such that SHA1(A) == SHA1(B)? If the answer is no than how can SHA1 be considered broken?

hash sha-1 collision-resistance  
asked by Andrew Tomazos 20 votes
answered by CodesInChaos 25 votes

How should I calculate the entropy of a password?

If part of the password is a whole regular English word, does the entropy of that part depend on the number of English words in existence, the number of English words known by the choosing algorithm, …

passwords entropy  
asked by this.josh 24 votes
answered by Thomas Pornin 23 votes

Can you answer these?

Challenge-response based on public-key decryption, why send public key

Quoting the handbook of applied cryptography, chapter 10.3.3 (i): Identification based on PK decryption and witness. Consider the following protocol: $A \leftarrow B: h(r), B, P_A(r,B)$ …

public-key authentication challenge-response  
asked by dubadu 2 votes

Symmetric-key login protocol

I'm trying to analyze a login protocol based on symmetric key cryptography. I'm just starting out, so this may very likely be a very bad idea, but nonetheless I'd like to hear your thoughts on it. …

protocol-design authentication symmetric  
asked by mpr 1 vote

Create multiple IV's from shared secret

I've answered a question on Stackoverflow which asked how to handle an IV after key agreement. One option I thought out for CBC was to use: Diffie-Hellman to create a secret; Create a symmetric key …

diffie-hellman cbc initialization-vector csprng  
asked by owlstead 1 vote
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