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Bigrams

Tool to analyze bigrams in a message. A bigram or digraph is an association of 2 characters, usually 2 letters, their frequency of appearance makes it possible to obtain information on a message.

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Bigrams -

Tag(s) : Cryptanalysis

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# Bigrams

## Bigrams Frequency Analysis

### Bigrams Parameters

 Analyze by Blocks (ABCDEF => AB,CD,EF) by sliding/overlapping (ABCDEF => AB,BC,CD,DE,EF)

### Action

 Compute Frequencies Count Appearances List missing letters/ngrams Count twin bigrams (AA, BB, …) Monoalphabetic Decryption

### What is a bigram? (Definition)

A bigram (or digram) is a pair of two characters, often 2 letters.

Example: AA or AB are bigrams

### How to analyse bigrams?

Bigrams are used in various encryptions in cryptography. There are 2 main modes of use of bigrams:

— A bigram may appear when a single character is encrypted by 2 characters.

Example: The Polybius cipher encodes each letter with a bigram representing coordinates in a grid. A can become BC

Encryptions that transforms grams into bigrams can be broken by retransforming then into a mono-alphabetic substitution.

— A bigram can come from the encryption of another bigram

Example: The Playfair cipher encodes the message by bigram by replacing it with another one. AB can become CD

### What are the most common bigrams in english?

The top 100 bigrams that appear in the english language are:

TH HE IN ER 2.9% 2.48% 1.87% 1.73% 1.65% 1.38% 1.35% 1.19% 1.17% 1.14% 1.13% 1.08% 1.08% 1.04% 1.01% 1% 0.96% 0.96% 0.94% 0.89% 0.89% 0.89% 0.88% 0.88% 0.85% 0.84% 0.82% 0.82% 0.8% 0.74% 0.73% 0.72% 0.68% 0.64% 0.64% 0.64% 0.63% 0.62% 0.62% 0.6% 0.59% 0.58% 0.58% 0.57% 0.57% 0.55% 0.52% 0.52% 0.52% 0.51% 0.5% 0.5% 0.49% 0.49% 0.49% 0.48% 0.48% 0.48% 0.47% 0.46% 0.46% 0.46% 0.46% 0.45% 0.45% 0.44% 0.44% 0.43% 0.42% 0.41% 0.41% 0.41% 0.4% 0.4% 0.39% 0.39% 0.39% 0.38% 0.38% 0.38% 0.38% 0.38% 0.37% 0.37% 0.36% 0.36% 0.36% 0.36% 0.36% 0.35% 0.34% 0.34% 0.34% 0.33% 0.33% 0.32% 0.32% 0.32% 0.32% 0.31%

### What is the difference between digram and bigram?

In english, digram and bigram means are the same thing: a couple of two characters. Bigram is the most common term.

## Source code

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Cite as source (bibliography):
Bigrams on dCode.fr [online website], retrieved on 2024-09-14, https://www.dcode.fr/bigrams

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