# What is Encryption?

> Encryption is the reversible cryptographic transformation of readable data, called plaintext, into ciphertext using an algorithm and cryptographic key.

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## Content

Its primary purpose is confidentiality: without the appropriate key, an unauthorized party should not be able to recover the original information.

Symmetric encryption uses a shared secret key for encryption and decryption. Asymmetric encryption uses a related public and private key pair and is commonly combined with symmetric encryption in practical protocols. Encryption may protect stored data or data moving between systems, but the actual protection depends on the complete implementation, including endpoint security, protocol design, algorithm and mode selection, and key management.

### Key points

- **Data at rest:** May protect storage devices, databases, files, backups, or selected fields against defined access and loss scenarios.
- **Data in transit:** Protocols such as correctly configured TLS can protect communications while they cross untrusted networks.
- **Integrity:** Encryption alone does not necessarily detect modification; authenticated encryption or a correctly composed integrity mechanism is often required.
- **Key lifecycle:** Secure generation, storage, distribution, rotation, recovery, revocation, backup, and destruction are central to the control.
- **Important limitation:** Encryption does not protect plaintext while an authorized or compromised endpoint can access it, and it does not by itself provide availability, erase metadata, or stop an authorized recipient from misusing data.

### Related terms

[Cryptography](<https://yellowcube.eu/glossary/cryptography/>) · [Cryptographic key management](<https://yellowcube.eu/glossary/cryptographic-key-management/>) · [Transport Layer Security (TLS) inspection](<https://yellowcube.eu/glossary/transport-layer-security-inspection/>) · [Data classification](<https://yellowcube.eu/glossary/data-classification/>) · [Data loss prevention (DLP)](<https://yellowcube.eu/glossary/data-loss-prevention/>) · [Pretty Good Privacy (PGP)](<https://yellowcube.eu/glossary/pretty-good-privacy/>)

### Sources

[NIST glossary: Encryption](https://csrc.nist.gov/glossary/term/encryption) · [NIST SP 800-57 Part 1 Rev. 5: Recommendation for Key Management](https://csrc.nist.gov/pubs/sp/800/57/pt1/r5/final) · [NIST SP 800-38D: Authenticated Encryption with GCM](https://csrc.nist.gov/pubs/sp/800/38/d/final)

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