## Overview#

Substitution Cipher is a method of Encryption by which units of plaintext are replaced with ciphertext according to a fixed system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth.

Substitution Cipher keeps the the units of the message are retained in the same sequence in the ciphertext, but the units themselves are altered.

Decryption the text by performing the inverse substitution.

Substitution Cipher can be compared with Transposition Ciphers where the units of the plaintext message are rearranged in a different and usually quite complex order, but the units themselves are left unchanged.

### More Information#

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