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).

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Applying differential cryptanalysis to ciphers with addition mod $2^{32}$

I am studying differential analysis and have a question. Consider the following simple cipher: $$c_1 = S(m_1 \oplus k_1) \oplus k_2$$ (Plaintext $m_1$ xor with key $K_1$, then result goes into an ...
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What does it mean when two encrypted files, encrypted with the same method but with different keys, when xor'd together, produce a repeating pattern?

Let's say I have fileA and fileB, both encrypted somehow, but in the same method with different keys. If I xor them together, they will make a repeating pattern of 32 bytes length. What does that ...
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The relationship between the key length and encrypt time in Xor algorithm?

I did work on the encryption algorithm and the decryption using the XOR method noticed that when more the key length, the less time spent on encryption and decryption. I have two questions in ...
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118 views

Reversing Rotation + XOR

I have this cypher which is as follows : Take 2 numbers : A=1011 and B=1010 if the ith bit of A is 1 then shift B i times to the left. So in the end you will get ...
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108 views

algebraic attacks for mixed operations (mod 2 and mod 256) [closed]

If a cipher has mixed operations, e.g $\oplus$ (addition mod $2$), and addition modulo $2^8$. How we we going to express them mathematically? Thanks in advance!
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Combined message separation

I have two ciphertexts, I suppose that its RC4 with reused key. I have XORed both ciphertexts and obtained message containing combined cleartexts. I suppose that the underlaying messages are written ...
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141 views

Do I need to keep a 64-bit version number secret?

Assume the following structure: version | iv | ciphertext | HMAC(version | iv | ciphertext | ..., key) The version starts out ...
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220 views

XOR cipher with three different ciphertexts and repeated key, key length known. How do I find the plaintexts?

Let us say we have three different plaintexts (all alphabets, A-Z): $x$, $y$ and $z$, each of length $21$. Let the key, $a$, be also of length $21$. Now, what we have is $x \oplus a$, $y \oplus a$ ...
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614 views

BruteForcer XOR (bfxor.exe) to attack 64-bit keys and longer

First of all, this is not a beginner's question since I already know a good deal about encryption and brute-force attacks. This is also no question on how to code programs for brute-force attacks ...
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387 views

randomly generated key reused with XOR

If I have a long randomly generated key (k), XORed with a message (m), but since the message is longer than the key, there is a chance of reusing the keystream with the same message, but the key is ...
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258 views

Encryption algorithms and the “One-Time pad” [duplicate]

I am not well versed in the field but I believe I know the basics. All encryption algorithms that I know of utilize direct data manipulation to encrypt a message (string of bits) such as shifting, ...
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93 views

Reducing the keyspace for a brute force attack on a chained 64-bit xor

I have a block of data which I know is encrypted using a chained 64-bit xor (sorry if that makes no sense, I'm not familiar with crypto lingo). I know a little bit about what the plaintext should look ...
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95 views

Is it possible to deduce the IV from CBC ciphered data, without knowing the key?

The question came up here, which left me thinking: Is it possible to deduce the IV from CBC ciphered data, without knowing the key? And if not, why is it considered a bad idea to create an IV by, for ...
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500 views

XOR secret sharing scheme

I was wondering how we can get a secret sharing of $a+b$ from the sharing of secrets $a$ and $b$ themselves by using an XOR secret sharing scheme, where $a_1,...,a_n$ and $b_1,...,b_n$ are the shares ...
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References for combining LFSRs with different lengths and taps?

I started learning streams ciphers with the use of LFSRs. Therefore, I tried to simulate what I am learning in a C sourcecode, which combines three registers and ...
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Binary equation with encryption

I'm trying to test the ring signature scheme proposed by Rivest Shamir and Tauman in the famous paper "How to leak a secret". One of the step consist in 4) the signer solves the following ring ...
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109 views

Is there specific name for simple XOR with ADD/SUB encoding?

Several years ago a group of malware authors began using code like this: for (j = 0; j < length; j++) ptr[j] = (ptr[j] ^ VALUEA) - VALUEB; for encoding, and ...
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246 views

Calculating XOR Key Sizes

I've been playing around with the Matasano crypto challenges (cryptopals.com). I had a couple false-starts on the challenge that has you creating a program to calculate the key size of a XOR encrypted ...
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Decrypt a message which is encrypted using XOR? [duplicate]

This is a puzzle asked in a contest. Given that encryption , decryption happens as per following rule/code: ...
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166 views

Split 32-bit LFSR into two 16-bit LFSR which xor to same sequence [duplicate]

Today I was thinking about exactly this. Is it possible, for a 32-bit LFSR e.g. ...
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51 views

Infer encoding mechanism from $n$-grams distance?

I have a series of obfuscated strings which across the set of strings have regions of high variance and regions of low variance – implying some encoding mechanism as opposed to an encryption procedure ...
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178 views

Linear transformation proof

Ok, so I have this question and I honestly have no idea how to prove it. I know that the function is linear and I know it works for every possible combination, I just don't know how to prove it in an ...
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Security of very simple XOR with random? [duplicate]

I am currently trying to implement a very fast and simple encryption algorithm in Lua for the purpose of using it with ComputerCraft. The main problem is that bitwise operations in Lua (5.2 at least) ...
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78 views

Why Might XOR's Lead to Hash Functions Lacking 2nd Pre-image Resistance?

My hash function is as follows: Cut the string in half (assume even length of 2m) XOR's the two halves together Take the result of the XOR and pass it to a function (a one-to-one and "onto" ...
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219 views

Is the keystream transmitted with the ciphertext when a stream cipher is used?

When a stream cipher is used and a keystream is generated to be XOR'ed with the plaintext, is the keystream sent with the ciphertext so that the receiver knows how to decrypt it? Or does the ...
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198 views

Repeated XOR decryption [closed]

I have this message in Hex: ...
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52 views

Can you identify this algorithm? [closed]

We are attempting to integrate our application in to a third party system. To do this we need to pass encrypted passwords in to this system. I have decompiled the assembly and looking at the code it ...
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70 views

Plain cascade and Xor cascade

I have seen in few places (mostly papers) talking about plain cascade and XOR cascade. I know what is cascade cipher is but I am not clear about what these are. Can anyone help to understand using ...
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314 views

XOR cipher Pseudo-random key strength

When implementing a XOR cipher with a pseudo-random key equal in length to the plaintext, Is there a significant difference in potential key strength between keys drawn from a pool of either 1000 or ...
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XOR of one-way function [migrated]

Considering the top answer to this question here, http://cs.stackexchange.com/a/10418, wouldn't this counter-example imply that we've inverted $f$? Consider the reduction where we take in $f(x_1)$ and ...
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Prove that complement of plaintext and the key, then ciphertext will be the complement of orig. ciphertext [duplicate]

I'm trying to prove in general terms the following: y = DESk(x) then.. y' = DESk'(x') I can plug in random variables for ...
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2answers
156 views

Reusing a one-time pad?

I have an embedded device. It produces larges files (200 MB). I want the device to encrypt the file before writing to disk, so I gave them all a 16-byte random key. How can I transform the large ...
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Key length requirement in a simple XOR implementation

I don't have much previous experience at all with cryptography, this is pretty much the first time I've tried anything similar. I'm trying to implement an extremely simple XOR encryption system in ...
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232 views

Is RC4 +XOR secure for small data?

I need to encrypt transmission between my device (with AVR processor) and base. I create packet data - it will be encrypted into string: ...
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One time pad in CBC mode?

I have been searching about if it is more secure to use CBC mode in OTP but I can't find anywhere where people have sad that it is more secure. Question: Is CBC mode in OTP more secure? Because I ...
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1 bit shannon entropy CPU instructions?

It has been proved, that the xor operator is suitable for entropy accumulation, due to its theoretical shannon entropy of 1 bit. There are six truth tables with ...
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XOR = Best encryption? [duplicate]

If you have a TRULY random key (in binary) and you have a text (in binary) that you want to encrypt. Can you simple XOR the key and the text? Is that secure? How secure?
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OTP - Reusing key IS SECURE! PROVED! [duplicate]

EDIT: This is not a duplicate, in this I have explained WHY this should be secure and not if it is secure, so please stop down-vote if you haven't read everything. I have questioned before about my ...