Questions tagged [block-cipher]
A block cipher is an encryption algorithm which encrypts fixed-size blocks of plaintext to same-sized blocks of ciphertext. For good ciphers every bit of the ciphertext block depends on every bit of the plaintext block and every bit of the key.
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Best public cryptanalysis of KeeLoq
KeeLoq is a proprietary 32-bit block, 64-bit key block cipher based on an 32-bit NLFSR and 64-bit FSR that is very frequently used for wireless car keys. It clocks its NLFSR for 528 rounds to encrypt ...
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Cryptanalytic research of North Korean block cipher Pilsung
I'd like to know if there are any papers which study the North Korean block cipher Pilsung. This block cipher is based heavily on AES, but with a few differences including a new key schedule based on ...
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Security considerations for permutation-based encryption using a Rubik’s Cube
I’ve been exploring a theoretical encryption method inspired by a 3×3 Rubik’s Cube.
Conceptually, it works like this:
The plaintext is written onto the cube’s faces in some systematic order. For ...
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Why same input and output mask in sm4 gives better approximation
SM4 is an unbalanced Feistel structure that takes a 128-bit plaintext and a 128-bit key as input and produces a 128-bit ciphertext as output. It consists of 32 rounds. In each round, only 32 bits are ...
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Bitslice Serpent Cipher - Should I apply Little Endian or Big Endian, Reversed bytes or not when loading key / text from NESSIE?
I'm implementing the Bitslice Serpent cipher using the Osvik's S-Boxes in C++. I read this answer which helped me validating my subkeys. However, the key given in the answer doesn't seem to be from ...
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Is this mode of operation likely to be recipe for unbreakable ciphers?
My basic idea was that one can use a CBC mode of operation, with the file's message digest as an IV:
The digest could then either be stored somewhere, or chaffed (dispersed) through the ciphertext, ...
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Practical applications of a block cipher tweak input
To my mind, there are two go-to uses for a tweak input for a block cipher or mode of operation:
A counter to make each block in a sequence of message blocks encrypt differently.
A counter for a ...
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Questions on PRINCE modes
PRINCE is a low-latecy 64-bit block cipher designed for/by NXP (I don't know if anyone else uses it). For instance, this dev board FRDM-MCXN947 has the following diagram
which shows the internal ...
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Clarification on Construction of the HATF and HOD Usage in "Revisiting Higher-Order Differential-Linear Attacks from an Algebraic Perspective"
I'm currently reading an interesting paper, "Revisiting Higher-Order Differential-Linear Attacks from an Algebraic Perspective", and I had a couple of questions in Section 4.1, which ...
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What's the minimum number of round keys in a secure block cipher?
Most block ciphers inject a round key after every round, but Threefish only injects a key every 4 rounds. Which made me thinking: what minimal number of key injections is needed for security?
I ...
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Reverse-engineering SQLite encryption: raw key known, but unable to extract decrypted DB
I've been working on a project for about a month now, and I'm completely new to the world of cryptography and reverse engineering. I'm just beginning to explore both static and dynamic analysis (with ...
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Insecure variants of Even-Mansour
This question comes from exercise 4.20 of Boneh and Shoup's "Graduate Course in Applied Cryptography [ver. 0.6]:"
Let $\pi: X\rightarrow X$ be a permutation, where $X=\{0,1\}^n$. Recall that ...
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Good key schedules for block ciphers
Out of all the block cipher key schedules in currently existence, which one(s) would be good to reuse in new block cipher designs? I've seen someone on here state that Rijndael's key schedule is a ...
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Camellia ECB-mode chosen key for desired ciphertext/plaintext pair
I am wondering if it is possible to find a K that decrypts a chosen ciphertext C into a chosen plaintext P in Camellia 128 ECB-mode? We can assume that there is no IV. There will exist some K that ...
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GCM AES over (wireless) internet - why reset counter with every packet?
I'm learning about block cipher operation modes and have a small question. I am listening to a lecture recording that casually mentions that when using Galois Counter Mode with AES over the internet (...
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