# All Questions

583 views

### Verify product without revealing multipliers

Situation: Several participants contribute encrypted random numbers. These numbers will be used to generate community-agreed random (by simple multiplication). Question: Is there any way to detect ...
545 views

### Why can't we use the first block of AES-CBC as MAC

As per topic, why can't we use the first block as MAC instead of using the last block? what's the rationale?
1k views

### breaking fully homomorphic encryption schemes

Fully homomorphic encryption schemes allow one to evaluate any arbitrary computation over encrypted data. Intuitively this seems to be too weak, irrespective of how we achieve this. An adversary who ...
488 views

### Advantages of 64-bit CPU smartphone

Advantages of having a 64-bit CPU vs 32-Bit CPU smartphone … 3. Complex Encryption. Improved Security: 64-Bit can process incredibly large numbers allowing you to better encrypt data against ...
3k views

### Initialization vector in symmetric-key encryption

Can we use symmetric-key algorithms without an initialization vector? I am making an app where both the sender and receiver share a key and there is no way to create an initialization vector for each ...
362 views

### Is it possible to work out the hash algorithm from a list of known message-hash pairs?

For example, in my situation I know hash(20) = 486e9638177faf1f34e49910491b77af. I also know the hashes for all values from 0 to 20. Is it possible to work out the ...
16k views

### Where i can find an AES implementation in python?

Where i can find a "reviewed" version of AES implementation in python. Not an API like PyCrypto whereby you can call AES algorithms in a single line.
965 views

### Tools for modelling and analysis of cryptographic protocols

I am designing some cryptographic protocols and I am new to it. Are there any well-known tools that can be used to model and design these protocols? And also verify or analyze their validity? If not ...
1k views

### Which is more secure using a CSPRNG for a One-time pad, or AES?

In reading about the One-time pad it appears to need truly random key for the pad. Since true random values are not practical to generate this presents a problem (thus making One-time pad less ...
3k views

### Different implementations of SHA1, which one is correct?

I have noticed that different implementations of SHA1 give different results. As I'm currently programming my own SHA1 implementation (in MATLAB / GNU Octave), I wonder which one should I follow? ...
400 views

### Is the new preprint “An Algorithm For Factoring Integers” by Yingpu Deng and Yanbin Pan worth reading?

I just discovered on the eprint server of the IACR the paper mentioned in the title. Scanning quickly over the paper I didn't find anything spectacular, so I doubt that their new(?) approach will be ...
572 views

### Is double hashing collision resistant?

Double hashing can surely provide more security than only one layer of hashing but does that necessarily mean it is more collision resistant? This question in a more mathematical form: If $H$ is a ...
583 views

### Can hashing become encrypting?

hashing some data and encrypting data share some similar attributes. Surely this is why "Difference between encrypting something and hashing something" has been asked. The point of this question is ...
1k views

### What are the differences between proofs based on simulation and proofs based on games?

what are the main pros and cons of proving the "security" of a crypto scheme under simulation proofs instead of game based proofs?
1k views

### How can I avoid calculating with huge numbers when implementing the RSA algorithm

There is 26-letter English alphabet. There is the plain text: TRYAGAINLATER. I need to encrypt it by RSA algorithm with the public key 53. What is the ciphertext? ...
207 views

### What is the difference between PBE and symmetric key encryption?

What is the difference between PBE (password based encryption) and symmetric-key algorithms? My understanding is that symmetric-key algorithms like AES and Twofish are used in PBE. Hence PBE is just ...
630 views

### Is it possible to apply hill-climbing algorithm to Diffie–Hellman?

If Eve intercepts all the values communicated between Alice and Bob in a Diffie–Hellman key exchange, and applies the hill-climbing algorithm to reverse the modulo function, how will the algorithm ...
2k views

### How long does it take to crack PBKDF2?

How much time will it take to crack PBKDF2 while using a 9 character password? I'm not specifying any specific system or platform. If a brute force attack is made using the best ever super computer ...
3k views

### Why is Serpent faster than AES in this benchmark?

I have a laptop without the AES-NI CPU instructions but with SSE4.1. I'm using Linux and tried the (in-memory) cryptsetup benchmark to get the rough tendency which returned: ...
452 views

### Is prime regeneration necessary for every new session using a Diffie-Hellman key exchange?

As I understand it, bruteforcing a Diffie-Hellman generated secret key takes $P-1$ attempts to crack the shared secret, where $P$ is a very large prime used for modulus. If your $P$ is quite large, ...
661 views

### How to avoid a chicken and egg scenario with encrypting passwords?

I am working on application that allows users to upload files containing company data and then share those files with a list of other users that have specific roles within the system. I want to ...
14k views

### SHA-256 and AES-128

Does it make an encrypted string more secure if I use SHA256(x) instead of x as the secret key for AES-128 encryption? I do know that SHA-256 produces 64 characters of hashed string regardless of what ...
643 views

### Can I pre-define the points in Shamir's Secret Sharing algorithm

With Shamir's secret sharing is it possible to pre-define the points returned by the algorithm? For simplicity if I have (k, n) where k=2, and n=4, and I have the points X,Y,Z, and Q. Can I create ...
2k views

### How do public key rings work in cryptographic applications?

I am wondering if there are any links to articles or resources available online, or explanations that you can give, that would help me to understand the concept of a public key ring, and why I might ...
2k views

### How can I break REDSHIRT / REDSHIRT2 encryption?

Recently, a user on Gaming.SE asked a question about whether the user password in the video game Uplink could be modified after being initially set. The game does not contain an option to change the ...
384 views

### Why not use an algorithm's code rather than data itself for one time pads?

Instead of using actual data for one time pads, what would be different if the code for an algorithm was exchanged so that to acquire the pad one would execute the algorithm and use its output? Why ...
368 views

### Can you help with that definition for a CCA?

The following is a definition taken from Introduction to Modern Cryptography by Katz and Lindell. I'm having a hard time understanding some basic concepts! Can you please help me? ...
261 views

### Which elliptic curves are quantum resistant? [closed]

If I want to learn about quantum resistant crytography what are the best resources? Which type of elliptic curves should I be studying?
277 views

### Is there any reason to use RSA or DSA when we have ECC?

I am having trouble coming up with a use case for RSA or DSA. It appears that ECC is better in every way. Is this true? I am looking for cases where RSA/DSA is superior to ECC, not where it is used ...
143 views

### Collision free one way function

I was playing with a function that I think is collision free and uninvertible assuming the hardness of integer factorization. I am unfortunately not as skilled at math as I would like to be, and do ...
842 views

### For any hash value, is there an infinite number of inputs that hash to it?

Bruce Schneier writes (back in 2005) in a post on cryptanalysis of SHA-1: SHA-1 produces a 160-bit hash. That is, every message hashes down to a 160-bit number. Given that there are an ...
760 views

### Practical Uses for Timing Attacks on Hash Comparisons (e.g. MD5)?

Consider the following code snippet: ...
378 views

### Key space vs Cardinality of 1024-bit RSA

I have been trying to figure out the encryption key space, and cardinality of 1024-bit RSA. From my understanding, the key generated from 1024-bit will be primes greater than $2^{1023}$ but less than ...
377 views