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).

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Decrypt cipher text with repeated XOR key

I got two cipher text that have been encrypted using XOR and the same key. The two cipher text as below. I would like to found what is the key in ASCII or hex Ciphertext 1 (in hexadecimal): 0d 69 1e ...
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Encryption algorithm [closed]

I do not have much knowlegde about cryptography. Can anyone please help me to answer this question: Having just completed a course in cryptography, Tom and Jerry start a new business to manufacture ...
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Example of a Two-party GMW Protocol

I have been looking for a concrete example of GMW protocol for two parties. I was trying with the following example for computing $XOR$ of two parties: A's secret bit is $a = 0$, B's secret bit is $b ...
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Using Diffie–Hellman without a key derivation function

In an answer to another question, it was suggested that the shared secret derived from Diffie–Hellman key exchange could then be used directly as a one-time pad to encrypt a message (by XORing the ...
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Meaning of difference Δ delta

I tried to understand some crypto text but I am new to this. Does this: Let $X,X'$ be $\ell$-bit values, and $\Delta X=X\oplus X'$ means that $X$ and $X'$ have $\ell$ bits and $\Delta X=X-X'$ or ...
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What does a repeated byte between two XORed hexadecimal ciphers mean?

I have two different hexadecimal strings (of same length) that I think are encoded plain text strings. Out of curiosity I XORed them and I found a single hex byte repeated for the length of the two ...
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How to reverse this simple xor encryption function? [closed]

this code decrypts encrypted rom code from an arcade game pcb (it is from source code of Mame emulator) for each byte in rom... ...
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Dining-Cryptographer Net (DC-Net) Scheme that Handles Collisions?

[Question edited at the request of Mods] I recently became fascinated with the elegant and simple solution that Chaum proposed for the Dining Cryptographers problem. If you are unfamiliar, please ...
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Solving a system of equations using both arithmetic and bitwise operations

At first I asked this question on Stackoverflow, where I was advised to ask here. So there is the question: I have a system of pretty simple equations: $x + y = A$ $f(x,y) + y = B$ $A, B$ are known....
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XOR PSK with random buffer

I need some guidance here: assuming I have the following: (PreSharedKey of 32 bytes) XOR (one time Random Buffer of 32 bytes) The only way to crack this should be brute forcing, correct? One of the ...
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Break an encryption made with XOR of a key and a known Nonce

My questions is general, but in my case regards the Kerberos protocol and the communication between the client first message and the KDC. Is there some problem in encrypting using a: (secret key XOR ...
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Is there any security issue if an attacker recovers the key stream generated by a stream cipher?

I've learned that a stream cipher like ChaCha20 generates a key stream that gets XORed with the plaintext to get the ciphertext... If an attacker knows the plaintext, he could just simply XOR that ...
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XOR of 16-bytes variables gives a result of size not equal to 16

I'm trying to write a XOR code for implementing CBC mode of operation from scratch but i seem to have some problem.The function takes two byte variables of 16bytes and the expected output should be ...
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Is there any vulnerability in this scheme?

We want to design a symmetric encryption scheme. Note that the following things are true for our system: The plaintext P will change every time for a given user. A user will choose a password which ...
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Why is the second XOR operation in OCB mode necessary?

In Rogaway's OCB mode, the offset (derived from the key) ist XOR-added twice: Once to the plaintext block, and a second time after the Encryption. I am wondering, why the second XOR operation is ...
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How secure is XOR-CBC?

How secure would this be? To be clear, I mean replacing the block cipher encryption step in the Wikipedia diagram explaining CBC with plain old XOR? EDIT: Replace ...
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Stream cipher - Many time pad

I understand the concept that when you xor the cipher texts you get the XOR messages cause the keys get XOR-ed and cancel out... This is at least the case when both the messages are of equal lengths. ...
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OTP Random Pad Renewal Without Extending Message

So I recently learned about the concept of a One Time Pad; and I from what I understand it means that if a XOR key is completely random and equal to or longer than the plaintext, it makes it so that ...
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PRNG XOR Pipeline

For an OTP I need the 'best' random data I can acquire. Please check if my thinking for stacking PRNGs together in a pipeline can only make the output statistically better, never worse?! So take a ...
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Key size of a repeating key XOR-encrypted message using Hamming distance

To find possible key sizes for an encrypted message, I break the message into blocks with length s, ...
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How strong is XOR encryption of 256 bit plain text with 256 bit key?

I was wondering if we take just 256 bits of plain text and simply XOR every bit with a 256 bit key, how strong can it be ?
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Would XOR'ing two Argon2 keys add extra security?

When a user registers on the app, they need to provide a password they create and we provide them with a randomly generated passphrase (e.g. Apple Cat Ladder Fire). We then use Libsodium's ...
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Simple block cipher

I came up with this concept, which I thought would be pretty secure. So the idea is this, you have a message $M$, which you split up in blocks of each 256 bits. You generate a random (pseudo-random ...
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Secret Sharing between $x$ parties

So for an unknown number of parties $x$, I make $x-1$ random $n$-bit strings represented by {$r_1, r_2,...,r_{x-1}$}. Where $s$ is the complete string split up between $x$ parties (yes?). I then ...
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Definition of diffusion matrix

I've been studying this article and since I'm not studying cryptography in English and it is not my native language, I don't understand some of the terminology. More precisely: what are diffusion ...
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ChaCha20: is this a potentially safe way of using nonce derived from private key if the key/nonce pair is never reused, for a given plaintext?

Note: I realize in ChaCha20 the nonce should be random and unique each time follow certain constraints but am trying to determine whether there could be a safe way to use it just once if other ...
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Why is this OTP decryption wrong? [closed]

i have a problem that goes: ...
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XOR and key reuse [duplicate]

I've been doing a bit of reading on the use of XOR and the dangers of key reuse. I'm aware that reusing a key can open a door for a frequency analysis attack on my plain text. So far, everything ...
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Circular hash collision where digest is pre-image: Could hash(a) = b, hash(b)=c, then hash(c)=a?

For any SHA-family of algorithms (including Keccak) except for SHA1, would it be theoretically possible for there to exist a pre-image a whose hash digest ...
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Does XOR'ing a random number with its inverse reduce its security if the result is a palindrome?

[And four related questions/examples below:] 2) If a random 256-bit number is XOR'ed with its reverse (i.e. the big-endian version XOR'ed with the little-endian version), does this reduce the ...
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How to handle multiple key-agreements

If I would use two different key-agreements e.g. SIDH and ECDH how would I handle these both derived keys? Is there a different between XOR or SHA-256 the two keys? (Would one reduce the level of ...
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Collision resistance of partial SHA-256 hashes XOR'ed

My hashing algorithm computes the SHA-256 for each of 12 input strings and XORs them to get the final hash. Is there a risk of an attacker being able to forge 2 sets of inputs that yield the same ...
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Can I use XOR to establish a longer shared secret?

SIKEp434 can only be used to encapsulate a 16 byte (128 bit) shared secret key. Most encryption algorithms these days (specifically (X)ChaCha20) require a 256 bit key to be secure, especially in a ...
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What's the number of unique possible Cayley tables in a 16*16 grid for XOR'ing single hex characters?

A few days ago, I designed and s-box then derived the following Cayley table of all possible XOR outputs of hex digits in the range of ${2^4}$ and was curious how many such "valid" possible ...
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OTP with fixed plaintext

I have just learned about the OTP, how it uses XOR, and how it's secure if the keys are random. But what will happen when the same plaintext is used again with a new key? $c_1 = k_1 ⊕ p$ $c_2 = k_2 ...
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How to find the key of XOR encryption in Java?

I am trying to find the key of an XOR-encrypted string in Java. It is very probable that the key is eight characters long. I have the encrypted string. I do not understand how to go backwards and ...
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What are linear and non-linear elements in cryptography?

I was reading this answer, How secure is XOR for encryption, and it stated that XOR's aren't good for securing messages as they are linear in Nature. And therefore should be paired with some non-...
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Hamming distance in xor decryption

I've been working on cryptopals 1.6, breaking xor and have got it working. I found this answer that explains why hamming distance works and I think after some thinking I believe I'm starting to ...
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Help understanding how to decrypt cipher

I am trying to create a padding oracle attack to decrypt a cipher that is encrypted with cbc and PKCS#7 padding. My first step is just to try and decrypt the second block. I have read a lot about it,...
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What are the implications of XORing ciphertext with plaintext?

I was intrigued by this question: Does adding complexity mean a more secure cipher? And it led me to wonder: What are the implications (if any) of XORing a ciphertext with the original plaintext ...
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How can I calculate the feasibility of brute-forcing missing secret shares against the secret checksum?

Secret sharing has the problem of player cheating, where a forged share $s'_i$ can be sent to generate a fake secret $m'$ during reconstruction (and the cheaters can even collude to generate the real ...
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How to determine if a generalized $\sigma$ function (similar to what is defined in SHA-2) is invertible?

Let $ROTR^n(x)$ and $SHR^n(x)$ denote the rotate right (circular right shift) and the right shift operations, as defined in SHA-2 standard. Consider any function of the form $$f(x) = ROTR^{n_1}(x) \...
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XOR operation to uncover plain-text out of given cipher-texts [duplicate]

I have a set of 11 hex coded strings that have been encrypted using XOR operation each with the same stream cipher key. How do I decrypt the 11th hex-coded string to arrive at the plain-text without ...
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Is there an efficient 2 out of 3 secret sharing scheme based on XOR?

I want to know if there is an efficient secret sharing scheme based on XOR such that a share of the message is given to three people and at least two must combine their share in order to construct the ...
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Storing secrets on a peer-to-peer network by splitting up AONT data

I've come up with a way to transform a stream of bytes such that if any single bit is modified, it cannot be transformed back into its original state. Here's how it works: Encoding Get hash ...
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Salsa20 Implementation: Sum of 2 Words with Carries Suppressed

I'm working on the 2nd part of the Salsa20 spec, and I want to implement a closure for the exclusive-or of two words(u32). The author defines the operation as the sum of two words with carries ...
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Why is this MAC flawed?

Consider a function to create a tamperproof cookie as follows: $$\text{cookie}(m, k) = m \| \text{hash}(m \oplus k)$$ where $m$ is a message provided by Alice, and k is a secret key known only to ...
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Reducing the XOR's in Implementation Cost

Suppose that we want to implement the following equations in binary finite field. $$ \begin{array}{l}\tag{1} y_{{1}}=x_{{1}}\oplus x_{{2}}\oplus x_{{7}}\oplus x_{{8}},\\ y_{{2}}=x_{{1}}\oplus x_{{2}}\...
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Multiplication instead of Key Derivation Function?

context In a one message communication. We are right after 2 DHKE (instead of one). Both users then have 2 secret numbers, J and K. question Is it a risk to replace the use of a Key Derivation ...
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Decrypt simple CBC with XOR

I have searched and my problem is exactly the same as shown here: Decrypt simple CBC message with known IV using XOR encryption However, when I implement the solution it doesn't work, neither does ...

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