encryption

Transformation of plaintext into ciphertext using a key, rendering data unreadable to anyone without the corresponding decryption key. The guardian of secrets in digital systems.

symmetric encryption

One key for both encryption and decryption. Fast, used for bulk data.

• AES (Advanced Encryption Standard): block cipher, 128/192/256-bit keys, dominant standard
• ChaCha20: stream cipher, used in TLS, fast in software

asymmetric encryption

Public key encrypts, private key decrypts. Enables secure communication without shared secrets.

• RSA: based on difficulty of factoring large primes
• elliptic curve cryptography (ECC): shorter keys, equivalent security, used in Bitcoin and cyber
• Diffie-Hellman: key exchange protocol, establishing shared secrets over public channels

hybrid approach

Asymmetric encryption exchanges a symmetric session key; symmetric encryption handles the data. TLS/HTTPS works this way.

applications

• secure communication: HTTPS, Signal protocol, end-to-end messaging
• digital signatures: proving authorship and integrity, authentication in cyber and bostrom
• disk encryption: protecting data at rest
• zero knowledge proofs: advanced cryptographic protocols built on encryption primitives

connections

Security relies on complexity theory — the hardness of factoring and discrete logarithm. compilers implement cryptographic libraries. consensus algorithms use encryption for message authentication.