# Questions tagged [notation]

Questions on the meaning, history, and usage of symbols and notation in cryptography. Please remember to mention where (book, paper, webpage, etc.) you encountered any notation you are asking about.

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### Carter-Wegman MAC different notations

While studying Carter-Wegman message authentication codes MAC, I got two different notations for the broader concept and have problems with understanding the difference, if any exist. Let $K, K_1, K_2$...
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### Does this protocol description and design look sound?

I am working on a tool that uses password derived keys for AES and a selectable modes of operation to encrypt (and later decrypt) text for storage on an insecure media. The tool is constrained to ...
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### Cartesian Product Notation for Encryption and Decryption

I'm learning about encryption $(E)$ and decryption $(D)$ algorithms and am wondering what the following notation means, specifically the cartesian product for $E$ and $D$. $k$ represents key, $P$ ...
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1 vote
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### Question about the notation $H\leftarrow\mathcal{H}_{\mathcal{K}}$ in an IND-CCA security experiment

In the paper "Hybrid Key Encapsulation Mechanisms and Authenticated Key Exchange" by Bindel et al., I looked at the IND-CCA security experiment (figure 3). In the first line of the game, ...
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### Understanding $\mathbb{Z}_q[X]/(X^N + 1)$ notation in cryptography paper

I can't seem to understand what $A_{N,q}$ represents in this paper (Section 2.1 - Notations). More specifically, I'm struggling to grasp the meaning of $\mathbb{Z}_q[X]/(X^N + 1)$. Could someone ...
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### What's the difference between these hash functions H, H1 and H2?

These are hash functions, but I don't understand their notations, can anyone tell me what's the difference between H, H1 and H2? $\mathbb{G}_1$ is an additive group and $\mathbb{G}_2$ is a ...
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### What the X stands for in the front of Elliptic curve names like X25519

I have seen Curve25519 and X25519, Curve448 and X448. I've seen a small note in this answer (Historical note: Originally, X25519 was called Curve25519, but now Curve25519 just means the elliptic ...
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### What does the "x" operator stands for in cryptography?

I am studying commitment scheme and in of the notes from the class this statement comes up. I'd like to know exactly what the X = M x R mean, since I don't seem to understand how the "x" operator ...
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### What is the meaning of the notation $\langle a, b\rangle$ in certain cryptography papers?

I'm trying to understand a paper from Brakerski and Vaikuntanathan. In it, they use the notation $\langle a,b \rangle$ but they don't explain what that means. The answers on this question say that it'...
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### How to interpret a specific mathematical notation in "FIPS 202" (SHA-3 / Keccak)

tl;dr What does "d <= |Z|" mean in the context of bit array manipulations? As a learning exercise I'm working on an implementation of SHA-3. I am not a cryptography specialist in any way but I ...
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1 vote
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### In DES : Matsui's notation(LC) vs Biham's notation(DC)

I'm doing linear attack for 8 rounds DES. And I just wondering about the difference between Matsui's notation and Biham's notation. In Matsui's paper, numbers bits from 0 to 63 from right to left. In ...
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1 vote
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### How to encrypt this using caesar cipher?

I recently had an exercise that read: Encrypt the message "easy question" using Caesar Cipher defined as: C=E(P)=(Pi+3) mod 26 What is this formula and how to solve it?
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