These include: 5 X 5 playfair cipher by Shang and Lu (2012). This makes frequency analysis much more difficult, since there are around 600 combinations instead of 26. It is a polygraphic substitution cipher, which encrypts pair of letters instead of single letters. The number of invertible matrices modulo 26 is the product of those two numbers. This work proposes an improved playfair encryption and decryption that will be hard to. The Playfair cipher was invented in 1854 by Charles Wheatstone, but named after lord Playfair who heavily promoted the use of the cipher. The cipher can, of course, be adapted to an alphabet with any number of letters all arithmetic just needs to be done modulo the number of letters instead of modulo 26.Ĭonsider the message 'ACT', and the key below (or GYB /NQK /URP in letters): Tool to decrypt/encrypt with Hill cipher, a ciphering system similar to affine cipher but using a coefficient matrix instead of 2 affine coefficients. In this cipher, each letter is represented by a number (eg. Hill Cipher is a cryptographic algorithm to encrypt and decrypt an alphabetic text.

In this post, we will discuss the Hill Cipher. The matrix used for encryption is the cipher key, and it should be chosen randomly from the set of invertible n × n matrices ( modulo 26). There are exceptions and some cipher systems may use slightly more, or fewer, characters when output versus the number that was input. To decrypt the message, each block is multiplied by the inverse of the matrix used for encryption. We also turn the plaintext into digraphs (or trigraphs) and each of these into a column vector. To encrypt a message, each block of n letters (considered as an n-component vector) is multiplied by an invertible n × n matrix, against modulus 26. To encrypt a message using the Hill Cipher we must first turn our keyword into a key matrix (a 2 x 2 matrix for working with digraphs, a 3 x 3 matrix for working with trigraphs, etc). Though this is not an essential feature of the cipher, this simple scheme is often used: The Beaufort Cipher is reciprocal (the encryption and decryption algorithms are the same). The plaintext letter is subtracted from the key letter instead of adding them. It is similar to the Vigenre cipher, but uses a different 'tabula recta'. Each letter is represented by a number modulo 26. The Beaufort Cipher is named after Sir Francis Beaufort.

Hill cipher decryption tool 5x5