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Public key encryption

(also public-key encryption, asymmetric encryption)

Public key encryption definition

Public key encryption is a cryptography method that uses two paired keys: a public key and a private key. In public key encryption, anyone can encrypt data using the recipient’s public key, but only the recipient can decrypt it using their private key — anyone else intercepting the data would see only gibberish.

Modern online security is built on security protocols that utilize public key encryption (like Transport Layer Security (TLS) and Secure Sockets Layer (SSL)). Public key encryption is used for email messaging, web browsing, and online banking — activities that have become indispensable in modern life.

See also: SSL Encryption, cryptographic key, end-to-end encryption, decryption, secret key

Public key encryption communications

  • Generation: The receiver generates a key pair — a public key and a private key. The public is shared with others wishing to communicate with the receiver, but the private key is kept secret.
  • Encryption: The sender encrypts their message to the receiver using the latter's public key.
  • Decryption: The receiver decrypts the encrypted message using their private key. Without this private key, the message is impenetrable to outside observers.
  • Reply: When the receiver wants to reply to the sender, the roles are reversed — the original receiver encrypts the reply using the original sender’s public key, who later decrypts it using their own private key.