Encryption fundamentals
Encryption is a technique in which plaintext is transformed into unreadable ciphertext using mathematical algorithms and keys. Two main categories of encryption exist:
- Symmetric encryption – the same secret key is used for both encryption and decryption. Common symmetric algorithms include the Advanced Encryption Standard (AES) and its predecessors DES and 3DES. AES is the current industry standard and comes in key lengths of 128‑, 192‑ and 256‑bits; a brute force attack on AES‑128 would take more than 100 trillion years with today’s computing power. Symmetric algorithms are efficient for bulk data encryption and are widely used for data at rest or in transit.
- Asymmetric encryption – a pair of mathematically related keys (public and private) is used. Algorithms like RSA and elliptic‑curve cryptography (ECC) belong to this category. RSA encryption is slower and generally used to encrypt small data or to encrypt symmetric session keys; modern systems combine RSA with AES by using RSA to secure AES keys during transmission.
Because symmetric keys must be shared securely and asymmetric encryption is computationally intensive, protocols such as TLS combine both: a public‑key handshake to establish a secure session key followed by efficient symmetric encryption. The TLS handshake uses asymmetric ciphers (RSA or Diffie‑Hellman/ECDH) to negotiate a shared secret; the subsequent data channel uses a symmetric cipher such as AES for confidentiality.
Cipher suites
A cipher suite is a set of algorithms used to secure a network connection. It typically specifies a key‑exchange algorithm, a bulk encryption algorithm, and a message authentication code (MAC) algorithm. TLS 1.3 restricts the number of supported cipher suites to improve security, and the handshake negotiates the strongest suite supported by both parties.
Encryption states: data in transit vs. at rest
- Data in transit – Information moving across networks must be encrypted to prevent eavesdropping. Protocols such as TLS set up a secure connection using asymmetric encryption for the handshake and a symmetric cipher for the data stream. TLS also provides integrity and authentication by verifying certificates and MACs.
- Data at rest – Data stored on disk or in databases should be encrypted to protect against physical theft and unauthorized access. AES 256‑bit encryption is recommended for data at rest, while AES 128‑bit is typically sufficient for data in transit. Best practices include strong random keys, key rotation, and separation of keys from encrypted data.
Types of encryption at rest
Full‑disk encryption (FDE)
FDE encrypts an entire storage device or partition using a single key. On Windows, BitLocker implements FDE; it encrypts entire volumes and uses a trusted platform module (TPM) plus a PIN or startup key to protect the key and require authentication during boot. Apple’s FileVault performs a similar role on macOS. FDE protects data at rest but does not protect data after the system is unlocked and can impact performance; once a device is unlocked, any user or process can read all data.
File‑based encryption (FBE)
FBE encrypts individual files with unique keys rather than an entire disk. This allows fine‑grained access control and protects data even if the device’s primary password is compromised. FBE supports selective sharing of encrypted files but is more complex to manage due to many keys and potential compatibility issues.
Virtual encrypted disks and container‑based encryption
Tools such as VeraCrypt create virtual encrypted disks inside a file or encrypt entire partitions. VeraCrypt supports features like LRW mode to enhance security and hidden volumes that appear as random data when unlocked.
Cloud encryption and zero‑knowledge architectures
Modern collaboration and storage services rely on encryption to protect data stored off‑site. Key topics include client‑side encryption, zero‑knowledge privacy and secure sharing:
- Folder Lock– provides client‑side encryption for cloud files. It supports more than 30 cloud providers, encrypts data locally using AES‑256 and RSA‑4096, and offers zero‑knowledge encryption so providers cannot decrypt files. It also includes single sign‑on and cross‑platform support, providing a virtual drive for encrypted file access.
- NordLocker – a zero‑knowledge cloud storage provider. It uses a combination of AES‑256, xChaCha20‑Poly1305 and Ed25519 to protect files. Files remain encrypted until unlocked by the user’s private key, enabling private file sharing across devices. NordLocker emphasises end‑to‑end encryption so that only the user can access the data.
- Zero‑knowledge encryption – a cryptographic technique that allows one party to prove knowledge of a secret without revealing the secret itself. Password managers like Bitwarden use zero‑knowledge architecture: data is encrypted locally, the provider never stores the master password, and keys are derived using PBKDF2; this provides end‑to‑end encryption and secure sharing. Zero‑knowledge methods enhance privacy, mitigate breach impact and help meet regulatory requirements.
Encryption for communications
Email encryption
- Transport Layer Security (TLS) – ensures that emails are encrypted in transit between mail servers, but it does not provide end‑to‑end protection; if the recipient’s server does not support TLS, messages fall back to clear text.
- Pretty Good Privacy (PGP) – uses asymmetric keys to sign and encrypt email content end‑to‑end. The sender encrypts the message with the recipient’s public key; the recipient decrypts it with their private key. GnuPG, an open‑source implementation, supports PGP and allows users to encrypt and sign data and communications. GnuPG emphasises privacy protection and has been used by journalists and whistleblowers.
- S/MIME – uses X.509 certificates to provide digital signatures and end‑to‑end encryption, enabling users to verify the sender’s identity and ensure integrity.
- StartTLS and DANE – StartTLS opportunistically upgrades plain SMTP connections to TLS but does not guarantee encryption; DNS‑based Authentication of Named Entities (DANE) verifies TLS certificates using DNSSEC to prevent man‑in‑the‑middle attacks.
Messaging protocols
Signal Protocol – an end‑to‑end encryption protocol used by apps like Signal, WhatsApp, Google Messages and Facebook Messenger. It combines a Triple Diffie‑Hellman handshake, prekeys and a Double Ratchet algorithm using cryptographic primitives (Curve25519, AES‑256, HMAC‑SHA256). The Double Ratchet algorithm derives a new key for every message to provide forward secrecy and break‑in recovery.
Key management and hardware security modules
Secure key management is essential for encryption software. Guidelines from the University of Texas at Austin emphasise that encryption keys protecting confidential data must themselves be treated as confidential and managed within a centralized key‑management infrastructure. Key management plans should ensure keys can be backed up (e.g., via escrow or recovery agents), rotated regularly, revoked upon compromise, and destroyed when no longer needed. Symmetric keys for confidential data must be randomly generated according to standards and rotated frequently: master keys at least annually, key‑encrypting keys twice per year and data‑encrypting keys every session or 24 hours.
Hardware security modules (HSMs)
An HSM is a physical computing device that safeguards and manages digital keys and performs cryptographic functions such as encryption, decryption and digital signatures. HSMs contain secure cryptoprocessor chips and can include tamper‑evident or tamper‑resistant packaging; they support features like clustering and failover for high availability. HSMs are used for key generation, storage and management, secure deletion of sensitive data and offloading asymmetric cryptographic operations. Common standards for HSM certification include FIPS 140‑3 and Common Criteria.
Cloud providers offer HSM‑as‑a‑Service (HSMaaS) to help organisations manage keys without purchasing hardware. The Cloud Security Alliance notes that HSMaaS solutions include hardware‑based random number generators, RAM, storage and an external interface. Organisations might choose HSMaaS to integrate with existing cloud infrastructure, obtain more control over key hierarchies and manage firmware or cryptographic libraries. Providers must implement strong physical and logical access controls and comply with standards like ISO 13491‑2 or PCI PIN. Customers should ensure device integrity, implement tamper‑resistance, enforce key lifecycle management, rotate and securely store keys, and maintain audit trails.
Read Also: The Impact of Open-Source Software on Computer Technology
Emerging encryption technologies
Homomorphic encryption
Homomorphic encryption is a form of encryption that allows computations to be performed directly on encrypted data without first decrypting it. The result, when decrypted, matches the output of operations performed on the plaintext. This technique enables privacy‑preserving outsourced computation and data analytics: for example, cloud services could process encrypted healthcare data without seeing patient information. Homomorphic encryption mitigates risks from processing data in clear text but may be vulnerable to side‑channel attacks and incurs significant computational overhead.
Secure multi‑party computation
Secure multi‑party computation (MPC) is a subfield of cryptography in which multiple parties jointly compute a function over their inputs while keeping those inputs private. Unlike traditional cryptography, which protects data from external adversaries, MPC protects participants’ privacy from each other; it allows, for instance, performing a joint calculation without revealing individual data values. MPC protocols have origins in the 1970s (e.g., mental poker) and matured in the 1980s; they often rely on secret sharing and zero‑knowledge proofs.
Quantum and post‑quantum cryptography
- Quantum cryptography exploits quantum mechanical properties to perform cryptographic tasks. Quantum key distribution (QKD) is the best‑known example; it provides an information‑theoretically secure method for two parties to exchange keys, relying on the no‑cloning theorem and the ability to detect eavesdropping. Quantum cryptography allows certain tasks that are impossible with classical communication and offers long‑term secrecy; QKD can theoretically protect data for up to 100 years, making it attractive for highly sensitive fields like healthcare and government.
- Post‑quantum cryptography (PQC) refers to classical cryptographic algorithms designed to resist quantum computing attacks. Traditional public‑key algorithms such as RSA and ECC rely on mathematical problems (integer factorization, discrete logarithm) that can be solved by Shor’s algorithm on a quantum computer. Because quantum computers capable of breaking current cryptography may appear within decades, PQC research focuses on lattice‑based, multivariate, hash‑based, code‑based and isogeny‑based cryptosystems. Cryptographers emphasise timely migration to PQC to counter “store‑now‑decrypt‑later” attacks. In August 2024, the U.S. National Institute of Standards and Technology (NIST) finalized its first three PQC standards (ML‑KEM for key agreement and ML‑DSA/SLH‑DSA for digital signatures); Cloudflare notes that post‑quantum key agreement is already being deployed by companies like Google, Apple, Meta and Signal.
Conclusion
Encryption software encompasses a broad range of techniques and technologies to protect data confidentiality, integrity and authenticity. Topics related to encryption include the choice of cryptographic algorithms (symmetric vs. asymmetric), data states (at rest, in transit and in use), storage encryption methods (full‑disk vs. file‑based), cloud encryption and zero‑knowledge services, communications protocols (email and messaging), key management and HSMs, and emerging technologies like homomorphic encryption, MPC and quantum‑safe cryptography. Understanding these related topics helps security professionals design robust systems that balance performance, usability and strong security.
