# Questions tagged [xor]

XOR, often written ⊕, is one of the basic operations on bits and bit-sequences. It is a building block of many cryptographic primitives (and some higher-level algorithms, like modes of operations).

279 questions
Filter by
Sorted by
Tagged with
84 views

### What is the name of this kind of logic diagram?

I want to read this kind of diagram, but I haven't found the name of this, or somewhere I can find a legend of symbols used, or a tutorial to learn reading this... I've googled this for over an hour, ...
• 23
1 vote
58 views

### What is the security of multiple encryption using Even–Mansour scheme (XEX)?

As I know, the best attack on single or double Even-Mansour scheme is N/2, being N the key size (or size of one of the two keys used). I know that encrypting two times using this scheme is susceptible ...
• 523
136 views

### Proof that the Family of Toeplitz Matrices is XOR-Universal

Definition of XOR-Universal hash functions by Abidin[1]: A class $H$ of hash functions from $M$ to $T$ is XOR-Universal$_2$ ($XU_2$) if there exist at most $|H|/|T|$ hash functions $h$ $\in$ $H$ such ...
207 views

### What does $(a+b) \bmod{256}$ and $a$ XOR $b$ reveal about $a, b$?

Say $a$ and $b$ are some uniform random $8$ bits so that the entropy of $a$ and $b$ is 8 bits each. If I show you $(a+b) \bmod{256}$ and $a$ XOR $b$, then what can you tell about $a$ and $b$? Or how ...
• 519
33 views

### Does random IVs in CTR block cipher mode combined with XOR allow to encrypt number of blocks up to the same numeric count of IV?

I read about CTR block cipher mode in Wikipedia: "If the IV/nonce is random, then they can be combined with the counter using any invertible operation (concatenation, addition, or XOR) to produce ...
• 523
1 vote
36 views

### What is the security of XORing SHAKE256_XOF with itself?

After reading "Can the xor of two RNG outputs ever be less secure than one of them?" I wondered if you can increase security of SHAKE256_XOF by using ...
• 165
153 views

### How can I decode a XOR cipher with a string key I know?

I have a text that has been XORed with the key "77U" (I am sure of this as it is a file created by a code I have, so I have seen every entry getting XORed by 77U. However, none of the online ...
• 3
29 views

### Is multiple encryption with XORs between each encryption operation susceptible to meet-in-the-middle attacks?

Let's suppose I take a cipher with key size equal to the block size (Threefish). I XOR a random block in the ciphertext, encrypt with a key, XOR another random block, encrypt again with another key ...
• 523
67 views

### Hamming distance between product and carry-less product

Motivation. There is a fast approximation to conventional multiplication. It conceptually works like long multiplication except for the fact that the carry is discarded instead of applied to the more ...
117 views

### Why is this code working

I was doing some introductory challenges at CryptoHack and one of the challenges, more precisely it was Favourite Byte, XOR with a single byte. I did my solution with XORing given string and single ...
89 views

### Does adding more XOR layers in the XEX block cipher mode increase its security or double it?

I read about XEX mode of operation in Wikipedia My question is: There are two keys that are XORed against plaintext, if instead of two XORed keys I add 4 or 6, does it increase the security of block ...
• 523
3k views

### What is wrong with XOR encryption with secure PRNG?

Suppose I want to encrypt a message with a password. Couldn't I just XOR the bytes with bytes from a cryptographically secure pseudorandom number generator (CSPRNG) with seed being the password, or a ...
• 141
955 views

### Nexor, an encryption algorithm that promises unlimited key sizes: Is it safe?

My intention is not to make spam here, but I came across this project in Github: https://github.com/andrewhodel/nexor It's an algorithm called Nexor, it promises encryption with unlimited key sizes. ...
• 523
Let $\mathbb{G}$ be a group of prime order $p$ with generator $g$. Suppose that I randomly pick $r_1,z_1 \leftarrow \mathbb{Z}_p$ and $r_2, z_2 \leftarrow \mathbb{Z}_p$ and $c \leftarrow \mathbb{G}$. ...