« Back to Glossary Index

Definition: What is a private key?

A private key is a collection of bits to set off algorithms for text encryption and decryption. It is created as part of public key cryptography during asymmetric-key encryption and used to decrypt and transform a message to a readable format. Public and private keys are paired for secure communication (learn more about Public Key).
A private key is also known as a secret key.

Explanation: What are private keys used for?

A private key is shared only with the key’s initiator, ensuring security. For example, A and B represent a message sender and message recipient, respectively. Each has its own pair of public and private keys. A (the message sender) sends a message to B. A’s message is encrypted with B’s public key, while B uses its private key to decrypt A’s received message.
A digital signature, or digital certificate, is used to ensure that A is the original message sender. To verify this, B uses the following steps:

  • B uses A’s public key to decrypt the digital signature, as A must previously use its private key to encrypt the digital signature or certificate.
  • If readable, the digital signature is authenticated with a certification authority (CA).

In short, sending encrypted messages requires that the sender use the recipient’s public key and its own private key for encryption of the digital certificate. Thus, the recipient uses its own private key for message decryption, whereas the sender’s public key is used for digital certificate decryption.

Applications of private keys

  • Digital signatures
  • Digital certificates
  • Public key cryptography
  • Cryptography
  • Encrypted messaging
  • Encrypted data exchanges
« Back to dictionary overview