Encryption definition
Encryption is the process of converting readable data, called plaintext, into an unreadable form, called ciphertext, using an algorithm and a key, so only parties with the correct key can decrypt it. It protects data stored on devices and servers and data moving across networks, forming a foundation of privacy, security and regulatory compliance.
How does encryption work?
An encryption algorithm, or cipher, combines data with a secret key through mathematical operations to produce ciphertext that looks random. Without the key, recovering the original data is computationally infeasible with a modern, properly implemented algorithm. Decryption reverses the process using the appropriate key. The algorithms themselves are public and heavily studied; security depends on keeping keys secret and using algorithms and modes correctly. Strong encryption also depends on good randomness, since predictable keys or nonces can be guessed.
Symmetric vs asymmetric encryption
Symmetric encryption uses the same key to encrypt and decrypt. It is fast and used for bulk data, with AES being the most widely used standard, often in GCM mode, alongside ChaCha20-Poly1305. The challenge is sharing the key securely between parties who need it. Key distribution is exactly the problem asymmetric encryption solves.
Asymmetric encryption uses a key pair: a public key that anyone can use to encrypt or verify, and a private key kept secret to decrypt or sign. RSA and elliptic-curve cryptography are common examples. Asymmetric operations are slower, so protocols like TLS use them to authenticate parties and agree on a shared symmetric key, then switch to symmetric encryption for the actual data. Post-quantum algorithms standardized by NIST, such as ML-KEM, are already deployed in hybrid TLS key exchange by major browsers and CDNs to prepare for future quantum computers.
Encryption at rest and in transit
Data needs protection in two main states, and most security standards and regulations expect both. Encryption is also increasingly applied to a third state, data in use, through confidential computing technologies that keep data encrypted in memory during processing. The common forms of encryption in everyday systems are listed below.
- In transit: TLS for websites and APIs, VPNs and SSH for network connections.
- At rest: full-disk encryption on laptops and phones, encrypted databases and storage.
- Application-level: encrypting specific sensitive fields, such as national ID numbers.
- End-to-end: only the communicating users can decrypt messages, not the service provider.
Why key management matters
Encryption is only as strong as the protection of its keys. Storing a key next to the data it protects, or hard-coding it in source code, makes encryption largely meaningless. Organizations use key management services, such as AWS KMS, Azure Key Vault and Google Cloud KMS, or hardware security modules to generate, store, rotate and control access to keys, with every use logged. Envelope encryption, where data keys are themselves encrypted by a master key, makes rotation and access control practical at scale.
Encryption and compliance
Regulations and standards such as GDPR, HIPAA, PCI DSS and India's DPDP Act expect appropriate security safeguards for personal and sensitive data, and encryption is one of the most commonly expected measures. Encrypted data that is lost or stolen is far less harmful, which can affect breach consequences under some laws. Nexzem builds encryption in transit, at rest and at field level into client applications, with keys managed through cloud key management services.