Cryptography & Security

Basic

Hamming Distance

Number of positions at which two strings differ.

Formula

d(x,y) = \sum_i [x_i \ne y_i]

Variables

dHamming distance

x_ii-th symbol of x

y_ii-th symbol of y

Example

1011 vs 1001: differ in one bit → d = 1

Did You Know?

Richard Hamming devised his distance in 1950 after weekend computer crashes kept wrecking his jobs.

cryptography hamming error coding

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More in Cryptography & Security

Modular Exponentiation

Core operation of RSA encryption — raise a message to a power, modulo n.

RSA Decryption

Recovers the message using the private exponent d.

Euler's Totient

Counts integers below n coprime to it, for n = pq — used to make RSA keys.

Shannon Entropy

Average information content — and the theoretical strength of a random source.

Password Entropy

Bits of security from password length and character-set size.

Key Space Size

Number of possible keys for a b-bit key.