Encryption
/ɪnˈkrɪp.ʃən/ · Noun · Security & Infosec
Definitions
Encryption is the process of converting readable data (plaintext) into an unreadable format (ciphertext) using a mathematical algorithm and a cryptographic key, so that only authorized parties with the correct decryption key can access the original information. Two main types exist: symmetric encryption (AES, ChaCha20), where the same key encrypts and decrypts, and asymmetric encryption (RSA, elliptic curve), which uses a public/private key pair. Encryption protects data at rest (stored files, databases), data in transit (HTTPS, TLS), and data in use. It is foundational to secure communication, digital signatures, password storage, and regulatory compliance frameworks like GDPR and HIPAA.
In plain English: Scrambling your data so that only someone with the right key can unscramble and read it — like writing in a secret code.
The two main types: symmetric encryption (AES — same key encrypts and decrypts, fast) and asymmetric encryption (RSA/ECC — public key encrypts, private key decrypts, slow). HTTPS uses both: asymmetric to exchange keys, then symmetric for the actual data transfer.
Example: 'All data at rest uses AES-256 encryption, and all data in transit uses TLS 1.3. End-to-end encryption means even we can't read user messages.'
Source: symmetric vs. asymmetric
Etymology
- c. 1900 BCE
- Egyptian scribes use non-standard hieroglyphs to obscure tomb inscriptions — the earliest known encryption
- c. 50 BCE
- Julius Caesar uses a simple substitution cipher (shift by 3) for military communications, later called the Caesar cipher
- 1976
- Whitfield Diffie and Martin Hellman publish 'New Directions in Cryptography,' inventing public-key cryptography
- 1991
- Phil Zimmermann releases PGP, bringing strong encryption to ordinary people and provoking a federal investigation
Origin Story
The ancient art of keeping secrets, now powered by mathematics
**Encryption** traces to antiquity -- the Caesar cipher (shifting letters by a fixed amount) dates to 58 BC. But modern encryption began with Claude Shannon's 1949 paper 'Communication Theory of Secrecy Systems,' which put cryptography on a rigorous mathematical foundation.
The revolution came in 1976 when Whitfield Diffie and Martin Hellman published 'New Directions in Cryptography,' introducing **public-key cryptography**. For the first time, two people could communicate securely without first sharing a secret key. RSA (1977) made it practical.
The U.S. government tried to control encryption as a munition through the 1990s 'Crypto Wars.' Phil Zimmermann was investigated for publishing PGP. Today, encryption protects every web connection (TLS), every messaging app (Signal Protocol), and every disk (BitLocker, FileVault). The crypto wars are back, with governments pushing for backdoors.
Coined by: Ancient practice; Claude Shannon (modern theory), Diffie-Hellman (public key)
Context: Shannon 1949, Diffie-Hellman 1976, RSA 1977
Fun fact: GCHQ's James Ellis, Clifford Cocks, and Malcolm Williamson actually invented public-key cryptography secretly in 1969-1973, years before Diffie-Hellman and RSA. But their work was classified and not revealed until 1997. Cocks independently discovered the RSA algorithm before Rivest, Shamir, and Adleman.