What Are Public Keys and Private Keys?
This article explains the core differences between public keys and private keys (encryption/decryption, publicity/confidentiality), details their generation logic based on RSA/ECC algorithms, their practical application scenarios in SSL certificates and digital signatures, and describes how Public Key Infrastructure (PKI) secures data transmission.
Overview of Public Keys
A public key, short for public cryptographic key, is a large numeric value used to encrypt data, and one of the keys in the key pair used for public-key cryptography. A public key is generated by software programs, or can be provided by a trusted designated authority (such as a Certificate Authority, CA), and made available to everyone through a publicly accessible repository or directory. A public key is usually paired with a private key that is known only to the owner of the public key. Public keys are primarily used to encrypt data and verify digital signatures.
Overview of Private Keys
A private key, short for private cryptographic key, is a variable used in cryptography to encrypt and decrypt data, and the other key in the public/private key pair. A private key is usually a long sequence of randomly or pseudorandomly generated bits, and can only be shared with the key generator or parties authorized to decrypt the data. Private keys are primarily used to decrypt data and create digital signatures.
Differences Between Public Keys and Private Keys
| Public Key | Private Key | |
|---|---|---|
| Accessibility | Public Obtainable by anyone | Confidential Known only to the holder |
| Key Type | Asymmetric | Asymmetric |
| Generation | Generated together with the private key | Generated together with the public key |
| Underlying Algorithm | Based on encryption algorithms such as RSA and ECC | Based on the same algorithm as the paired public key |
| Function | Encrypts data and verifies digital signatures | Decrypts data and creates digital signatures |
| Security Requirements | No special requirements | Must be kept strictly confidential to prevent disclosure |
| Storage Location | Stored in digital certificates, outgoing emails and executable files | Stored on authorized devices and non-public servers |
| Common Use Cases | SSL certificates, blockchain | Secure transactions, authentication |