Editing Block cipher (section)

{{Short description|Type of cipher}}
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In [[cryptography]], a '''block cipher''' is a [[deterministic algorithm]] that operates on fixed-length groups of [[bit]]s, called ''blocks''. Block ciphers are the elementary [[cryptographic primitive|building blocks]] of many [[cryptographic protocol]]s. They are ubiquitous in the storage and exchange of data, where such data is secured and authenticated via [[encryption]].

A block cipher uses blocks as an unvarying transformation. Even a secure block cipher is suitable for the encryption of only a single block of data at a time, using a fixed key. A multitude of [[block cipher modes of operation|modes of operation]] have been designed to allow their repeated use in a secure way to achieve the security goals of confidentiality and [[authentication|authenticity]]. However, block ciphers may also feature as building blocks in other cryptographic protocols, such as [[universal hash function]]s and [[pseudorandom number generator]]s.