Cryptography is the technical foundation that makes confidentiality, integrity, authentication, and non-repudiation possible on the internet. A hash is a one-way function that converts data into a fixed-size string, useful for verifying integrity and storing passwords safely. Encryption converts plaintext into ciphertext to protect confidentiality, and decryption reverses the process using a key. In symmetric encryption the same key is used for both directions, and AES, the Advanced Encryption Standard, is the most widely deployed symmetric algorithm. Asymmetric encryption instead uses a public and private key pair, enabling operations such as secure key exchange and digital signatures; RSA and elliptic curve cryptography (ECC) are the dominant asymmetric algorithms.
These primitives combine into trust systems. A digital signature is a cryptographic method that verifies both the authenticity and the integrity of a message, typically by signing a hash with a private key. A digital certificate is an electronic document that binds a public key to an identity, and it is issued by a trusted Certificate Authority (CA). Public Key Infrastructure (PKI) is the overall framework of standards, processes, and software used to manage certificates across an organization or the internet. End-to-end encryption is the property where only the communicating parties can read messages, and forward secrecy ensures that session keys remain safe even if a long-term private key is later compromised.
These cryptographic tools are deployed through widely used protocols. TLS (Transport Layer Security) is the modern standard for encrypted communication on the web and the successor to the now-deprecated SSL. When web traffic is sent over TLS, it is called HTTPS, and supporting headers such as HSTS force browsers to use HTTPS. Virtual Private Networks (VPNs) create encrypted tunnels for secure remote access into private networks. Hardware-backed cryptography is used in higher-assurance settings: a Hardware Security Module (HSM) is a dedicated device for cryptographic operations, services like AWS KMS manage keys in the cloud, and standards such as FIPS 140-2/3 certify that cryptographic modules meet government security requirements.