keypairs

A keypair in public-key cryptography is a pair of related cryptographic keys: a public key and a private key. The public key is intended to be distributed or shared openly, while the private key must be kept secret by its owner. The two keys are mathematically linked so that operations performed with one key can be verified or complemented by the other. Keypairs enable three core capabilities: confidentiality (encryption with the recipient’s public key), authenticity and integrity (digital signing with the sender’s private key), and secure key exchange (establishing a shared secret for symmetric encryption).

Keypairs are typically generated together using algorithms such as RSA, elliptic curve cryptography (including ECDSA and ECDH), or Ed25519. RSA relies on the difficulty of factoring large numbers, while ECC-based schemes use properties of elliptic curves to achieve comparable security with smaller key sizes. Public keys may be stored or transmitted in formats such as PEM, DER, or OpenSSH and can also be represented as blockchain addresses or certificates.

Common uses include securing communications and authentication. In SSH, a user’s public key is installed on a server to allow passwordless login, while the client proves possession of the corresponding private key. In TLS, servers (and sometimes clients) present a public key certificate to establish a secure channel. Public-key cryptography underpins email encryption (PGP/S/MIME), code signing, and various authentication and digital-signature workflows. In blockchain and cryptocurrency systems, public keys derive addresses used to receive funds, while private keys authorize spending.

Security considerations emphasize protecting private keys through encryption-at-rest, passphrases, and hardware security modules, as well as regular key rotation, backup, revocation, and proper lifecycle management.