# All Questions

159 views

### Probability of Repeated Encrypted Block In Output Feedback (OFB) Mode

Is there any probability/chances of repeated encrypted block in Output Feedback (OFB) mode? Is there any existing documentation/studies about that? If it is existing, can you please provide me a link ...
963 views

327 views

### Is symmetric encryption vulnerable to plain-text-attacks?

Imagine that Bob sends a message to Alice for symmetric encryption to send to Charlie. (Only Alice and Charlie know the key.) Alice sends the encrypted message back to Bob to send to Charlie. Can Bob ...
951 views

### What is the signature scheme with the fastest batch verification protocol for multiple signers?

I'm looking for a scheme where signing may be costly (slow) but batch verification with different signers is the fastest possible. Modified ECDSA allows batch verification for different signers with ...
910 views

### Why Addition Mod 32?

I was looking at the algorithm for Twofish, and I noticed that in some places a XOR is used, but in others, they use "addition modulo-32." What makes modulo-32 special? Why not always use XOR? Why not ...
435 views

### Toy cipher — does it have a name?

When I was perhaps nine years, I borrowed a book from the library on various maths and CS topics. It outlined various simple ciphers, including one that I used a lot, just for fun. I can't remember ...
6k views

### HMAC vs MAC functions

I've read definitions of MAC and HMAC, but can't say I've completely grasped the differences. What are principle differences? When to use one and when the other?(Typical Use Cases)
180 views

### How can the Schmidt–Samoa cryptosystem uniquely decrypt large messages?

Suppose I choose $p=7$ and $q=11$. This gives a public key of $p^2·q = 539$. However, decryption occurs using a modulus of $p·q=77$. If a person chooses to encrypt $500$ using my public key, how ...
232 views

### DGK Cryptosystem Key Generation and Decryption Issues

I detailed here the DGK (Ivan Damgård, Martin Geisler and Mikkel Krøigaard) cryptosystem, and I managed to get it to work, most of the time... The BIG problem that I am facing at the moment is that ...
7k views

### Difference between encrypting something and hashing something

What is the difference between encrypting something and hashing something? in what situations would I want one or the other?
230 views

### Where can i find relative software for differential cryptanalysis?

Is there any publicly known software for differential cryptanalysis over some cryptographic building blocks as blocks ciphers or cryptographic hash functions
2k views

### How do digital certificates work, and why is it not possible to reverse engineer one from a signed file?

Digital certificates are used quite commonly these days, for signing files. They are used by various operating systems to ensure reliability and security. For example, Android requires that each of ...
5k views

### What are the benefits of the two permutation tables in DES?

Why do we use a permutation table in the first step of DES algorithm and one at the end of algorithm?