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Questions tagged [key-schedule]

A key schedule is an algorithm that expands a relatively short master key to a relatively large expanded key for later use in an encryption and decryption algorithm.

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Is the key schedule of Serpent a circle?

The creation of the prekeys for Serpent works by XORing some previous values with a counter and a fixed value. Every word is 32 bits big and 4 words form a round key (after applying a S-Box, but this ...
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search of patterns in key schedules

I am developing a new key schedule, and there is this article (Enhanced Key Expansion for AES-256 by Using Even-Odd Method) where the authors also propose a new algorithm and one of the objectives is ...
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How can I find or reverse engineer the whitening in an AES algorithm?

I am working with this black box cryptography scheme. I know the plain text, cipher text, and everything else except how they whiten the data (or key?). Everything is 128 bit, 16 bytes. I have two ...
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Is uneven DES keybit use exploitable?

Question: Is there any cryptanalytic leverage to be had from the fact that some of the 56 "raw" keybits of DES are used more & less often than others? Observation: over the course of the 16 ...
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Optimizing the AES key schedule when round keys cannot be cached

I have an implementation of AES which can cache at most a 256-bit value between encryptions. Currently, the master key is cached and the key schedule is re-computed for each and every block. Is there ...
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Difference in the key schedule of AES for decryption given different orders of operation

As per the Stallings book, the normal decryption of AES has different sequence of transformations [method 1 below], which leads to two separate software or firmware modules and that is undesirable. ...
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Programming Interface: Preparing Key Schedule for Both Encryption and Decryption

Quick question (01): what is the uniform interface for a symmetric block cipher? Is it $(f:k \to k', enc_{k'}:c \to p, dec_{k'}:p \to c)$ or $(f:k \to k_e, g:k \to k_d, enc_{k_e}:c \to p, dec_{k_d}:...
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Attack on Cipher with Highly Related RoundKeys

Consider a variation of AES with modified Key-Schedule and following observation on the Key Schedule. If there exist a relation d between two Master keys, the key schedule is so weak that all sub-...
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Triple DES: Does knowing the plaintext limit my keyspace for brute force?

My goal is to try and decrypt a single 8 byte block of a Triple DES encrypted data block and in doing so discovering the 8 byte keys that were used. This is mostly an academic exercise but could ...