> For the complete documentation index, see [llms.txt](https://wiki.songer.pro/interviewing/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.songer.pro/interviewing/security-domains-and-technical-aptitude/cryptographic-protections/cryptography/what-are-block-and-stream-ciphers.md).

# What are block and stream ciphers?

Block ciphers are algorithms that encrypt data in fixed-length blocks, such as 16-byte or 64-byte blocks. These ciphers use one or more keys to encrypt and decrypt the data. Stream ciphers, on the other hand, encrypt data one bit or one byte at a time. They tend to be faster and more efficient than block ciphers, but they are also more vulnerable to attack.