Changing some part of the plain text for some matching part of cipher text. Historical algorithms typically use this.

Substitution

https://en.wikipedia.org/wiki/Substitution_cipher

In cryptography, a substitution cipher is a method of encrypting 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. The receiver

deciphers the text by performing the inverse substitution.

Incorrect answers:

Decoding - the reverse process from encoding - converting the encoded message back into its

plaintext format.

Collision - occurs when a hash function generates the same output for different inputs.

Transposition - a method of encryption by which the positions held by units of plaintext (which are

commonly characters or groups of characters) are shifted according to a regular system, so that the

ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed (the

plaintext is reordered). Mathematically a bijective function is used on the characters' positions to

encrypt and an inverse function to decrypt.