● 131 entries

Cryptography

AEAD (Authenticated Encryption with Associated Data)A symmetric encryption primitive that provides confidentiality, integrity, and authenticity in one operation, with the ability to bind unencrypted 'associated data' (headers, routing info) to the ciphertext's authentication tag.
AES (Advanced Encryption Standard)A NIST-standardized 128-bit block cipher with 128-, 192- or 256-bit keys, designed by Daemen and Rijmen and used as the dominant symmetric cipher worldwide.
AES-CBCAn unauthenticated block-cipher mode that chains AES encryption with the previous ciphertext block; vulnerable to padding-oracle attacks when used without a MAC.
AES-CTRA stream-cipher mode that turns AES into a keystream generator by encrypting an incrementing counter and XORing the output with the plaintext.
AES-GCMAn authenticated encryption mode that combines AES in counter mode with a GHASH-based authentication tag for confidentiality and integrity in a single pass.
AMD SEV / SEV-SNPAMD EPYC technology that encrypts and integrity-protects each virtual machine's memory, isolating guests from a malicious or compromised hypervisor.
AppArmorA path-based mandatory access control system for Linux, used by Ubuntu and SUSE as a simpler alternative to SELinux for confining individual programs.
Argon2A modern memory-hard password hashing function and KDF, winner of the 2015 Password Hashing Competition and specified in RFC 9106.
ARM TrustZoneA hardware security extension on ARM CPUs that partitions the SoC into a Secure World and a Normal World, providing a TEE for keys, DRM, and biometric data.
ASN.1Abstract Syntax Notation One: an ITU-T standard (X.680 series) that describes data structures used in cryptography and telecoms in a language-independent way.
Asymmetric EncryptionA cryptographic scheme that uses mathematically linked key pairs — a public key for encryption and a private key for decryption — to enable secure communication without prior secret sharing.
Attribute-Based EncryptionPublic-key encryption (Sahai/Waters 2005) where ciphertexts and keys are linked to attributes and policies, so decryption succeeds only if the policy is satisfied.
BB84 ProtocolThe first quantum key distribution protocol, proposed by Bennett and Brassard in 1984, which encodes random bits on photon polarization states.
bcryptAn adaptive password-hashing function based on the Blowfish cipher with a tunable cost factor, designed by Provos and Mazières in 1999.
BLAKE2A fast, modern cryptographic hash function specified in RFC 7693, offering security comparable to SHA-3 with significantly higher performance in software.
Block CipherA symmetric cipher that encrypts fixed-size blocks of plaintext with a secret key, usually combined with a mode of operation to handle data of arbitrary length.
BlowfishA 64-bit-block, variable-key-length Feistel cipher designed by Bruce Schneier in 1993; secure cryptanalytically but limited by a small block size and superseded by AES.
BLS SignatureA short pairing-based digital signature by Boneh, Lynn, and Shacham (2001) supporting deterministic single signatures and efficient aggregation across many signers.
CAC (Common Access Card)The smart-card identity credential issued by the US Department of Defense to military, civilian and contractor personnel for physical and logical access.
ChaCha20A modern stream cipher designed by Daniel J. Bernstein, using a 256-bit key and 96-bit nonce, widely deployed alongside Poly1305 as the AEAD ChaCha20-Poly1305.
ChaCha20-Poly1305An AEAD construction pairing the ChaCha20 stream cipher with the Poly1305 one-time authenticator, standardised in RFC 8439 for TLS 1.3 and WireGuard.
CipherAlgorithm that transforms plaintext into ciphertext (encryption) and back (decryption), parameterized by one or more cryptographic keys.
Cipher SuiteA named combination of cryptographic algorithms — key exchange, authentication, bulk encryption, and integrity — negotiated by protocols such as TLS for a given session.
CiphertextOutput of an encryption algorithm: data that should be unintelligible to anyone without the correct key.
COSECBOR Object Signing and Encryption (RFC 9052) is the binary, CBOR-based counterpart to JOSE, designed for constrained IoT devices and modern protocols.
Cryptographic AgilityThe property of a system that lets it replace cryptographic algorithms, parameters, or keys quickly and safely when threats or standards change.
Cryptographic ErasureRendering encrypted data unrecoverable by securely destroying the encryption keys instead of overwriting the storage media itself.
Cryptographic Hash FunctionA deterministic one-way function that maps arbitrary-length input to a fixed-length digest, designed to be collision-, preimage-, and second-preimage-resistant.
Cryptographic KeyA high-entropy secret or public value that parameterizes a cryptographic algorithm to encrypt, decrypt, sign or authenticate data.
CryptographyThe science of securing information through mathematical techniques that provide confidentiality, integrity, authenticity, and non-repudiation in the presence of adversaries.
CRYSTALS-DilithiumA lattice-based digital-signature scheme standardized by NIST as FIPS 204 (ML-DSA) in August 2024 and intended as the post-quantum replacement for RSA, DSA, and ECDSA signatures.
CRYSTALS-KyberA lattice-based key-encapsulation mechanism standardized by NIST as FIPS 203 (ML-KEM) in August 2024, designed to replace RSA and Diffie-Hellman key exchange in a post-quantum world.
Curve25519A Montgomery elliptic curve designed by Daniel J. Bernstein, used in the X25519 Diffie-Hellman function specified in RFC 7748 with ~128-bit security.
DecryptionThe reverse cryptographic operation that converts ciphertext back into its original plaintext using the appropriate algorithm and key.
DES (Data Encryption Standard)An obsolete 64-bit block cipher with a 56-bit key, standardized by NBS in 1977 and now considered broken because its key space can be exhausted in hours.
Diffie–Hellman Key ExchangeA public-key protocol that lets two parties derive a shared secret over an insecure channel without ever transmitting it, based on the difficulty of the discrete logarithm problem.
Digital SignatureA public-key cryptographic mechanism that proves the authenticity, integrity and non-repudiation of a message or document.
ECDHThe elliptic-curve variant of the Diffie–Hellman key-exchange protocol, providing the same shared-secret functionality with smaller keys and faster operations.
ECDSAThe elliptic-curve variant of the Digital Signature Algorithm, standardized in FIPS 186, producing compact signatures whose security relies on the elliptic-curve discrete logarithm problem.
Ed25519An EdDSA signature scheme over the twisted Edwards curve edwards25519, offering ~128-bit security with deterministic, fast, side-channel-resistant signing as defined in RFC 8032.
Elliptic Curve Cryptography (ECC)A family of public-key algorithms based on the algebraic structure of elliptic curves over finite fields, offering equivalent security to RSA with much smaller keys.
EncryptionThe cryptographic transformation of plaintext into ciphertext using an algorithm and key so that only authorized parties can recover the original data.
Envelope EncryptionA pattern in which bulk data is encrypted by a fast data encryption key, which is itself encrypted (wrapped) by a master key stored in a KMS or HSM.
Falcon (Signature Scheme)A lattice-based post-quantum signature scheme over NTRU lattices, selected by NIST in 2022 for compact signatures and now being finalized as FIPS 206 (FN-DSA).
Federated LearningA distributed machine-learning paradigm in which many clients collaboratively train a model under a central coordinator while keeping their raw data on-device.
FIDO Security KeyA hardware authenticator that uses the FIDO U2F or FIDO2/WebAuthn standards to perform phishing-resistant, public-key-based authentication to web and enterprise services.
FIPS 140 / FIPS 140-3US federal standard, maintained by NIST, that defines security requirements for cryptographic modules and their certification through accredited labs.
Glitch AttackA fault-injection technique that briefly perturbs voltage or clock signals to make a chip skip instructions or leak cryptographic secrets.
Grover's AlgorithmA quantum search algorithm that finds a marked item in an unstructured database of N entries in roughly sqrt(N) steps, providing a quadratic speed-up against symmetric ciphers and hash functions.
Hardware AttestationA cryptographic protocol by which a device proves its identity and software measurements to a remote verifier using a key rooted in tamper-resistant hardware.
Hardware Security Module (HSM)Tamper-resistant hardware appliance that generates, stores, and uses cryptographic keys without ever exposing the raw key material to the operating system.
Hardware TokenPhysical device that stores cryptographic secrets and performs authentication operations, used as a possession factor in multi-factor authentication.
Harvest Now, Decrypt LaterAn attack strategy where adversaries record encrypted traffic today to decrypt it once cryptographically relevant quantum computers become available.
Hash CollisionTwo distinct inputs that produce the same cryptographic hash value, breaking integrity, uniqueness, and signature guarantees that depend on the hash function.
HKDF (HMAC-based Key Derivation Function)An extract-then-expand key derivation function based on HMAC, specified in RFC 5869, designed to turn high-entropy but non-uniform secret material (DH shared secrets, master keys) into multiple cryptographically strong keys.
HMACA keyed Message Authentication Code construction built on top of a cryptographic hash function, defined in RFC 2104 and FIPS 198-1.
Homomorphic EncryptionAn encryption scheme that allows computations to be performed directly on ciphertexts, producing encrypted results that match the operations on the underlying plaintexts.
Identity-Based EncryptionPublic-key encryption where an arbitrary identifier (email, phone) serves as the public key, with private keys issued by a trusted Private Key Generator (Boneh/Franklin 2001).
Initialization Vector (IV)A randomized starting value for a block-cipher mode of operation that ensures identical plaintexts encrypted under the same key yield different ciphertexts.
Intel SGXIntel Software Guard Extensions, a CPU instruction set that creates encrypted memory enclaves to protect code and data from a compromised OS or hypervisor.
JOSEJavaScript Object Signing and Encryption: an IETF family of standards (RFC 7515-7520 and 8037) for representing signed and encrypted data using JSON.
JWEJSON Web Encryption (RFC 7516) is a JOSE format that confidentially encapsulates a payload using authenticated encryption and either a key-wrapping or key-agreement scheme.
JWKJSON Web Key, defined in RFC 7517, is a JSON object that represents a public or private cryptographic key for use in JOSE and OAuth-family protocols.
JWSJSON Web Signature (RFC 7515) is a JOSE format that protects the integrity and origin of arbitrary content using a digital signature or MAC over a Base64URL-encoded header and payload.
Key Derivation Function (KDF)A cryptographic function that derives one or more strong cryptographic keys from a secret input such as a password, shared secret or master key.
Key EscrowAn arrangement in which copies of cryptographic keys are stored with a trusted third party so they can be recovered by authorized entities under defined conditions.
Key Management SystemA centralised service that generates, stores, rotates, and audits cryptographic keys on behalf of applications, typically backed by hardware security modules.
Key RotationThe periodic replacement of cryptographic keys with new ones to limit the volume of data protected by any single key and contain the impact of compromise.
Lattice-Based CryptographyA family of post-quantum cryptographic schemes whose security reduces to the hardness of finding short vectors or solving linear equations with small errors over high-dimensional lattices.
Master KeyA high-value long-term key from which other cryptographic keys are derived or which directly encrypts other keys.
MD5A 128-bit cryptographic hash function designed by Ron Rivest in 1992; now broken — practical collisions are trivial and it must not be used for any security-sensitive purpose.
Message Authentication Code (MAC)A short symmetric-key tag that authenticates a message and detects tampering, computed and verified with the same shared secret.
Microsoft PlutonA Microsoft-designed security processor integrated into the CPU die that implements a firmware TPM 2.0, key isolation, and identity attestation for Windows 11.
ML-DSA (FIPS 204)NIST's standardized post-quantum digital signature algorithm, derived from CRYSTALS-Dilithium and published as FIPS 204 in August 2024 — the default lattice-based PQ signature for code signing, X.509, and DNSSEC over time.
ML-KEM (FIPS 203)NIST's standardized post-quantum key encapsulation mechanism, based on the CRYSTALS-Kyber design and published as FIPS 203 in August 2024 — now the default PQ KEM for TLS, IPsec, and hybrid key exchange.
NFC Relay AttackA real-time man-in-the-middle attack that tunnels NFC traffic between a victim's card and a remote reader so the attacker can use the card from a distance.
NIST PQC StandardizationThe multi-year NIST process that selects and standardizes post-quantum cryptographic algorithms; its first three standards, FIPS 203, 204, and 205, were published in August 2024.
NitrokeyAn open-source security key from German vendor Nitrokey GmbH that provides FIDO2, OpenPGP, X.509 smart-card and OTP functionality in a USB token.
Noise Protocol FrameworkA composable framework by Trevor Perrin for building modern, formally analyzable secure channel protocols out of Diffie-Hellman, HKDF, and AEAD — the cryptographic core of WireGuard, Signal's I/O Pipe, and many newer protocols.
NonceA "number used once" supplied to a cryptographic algorithm to guarantee freshness and prevent replay or key/IV reuse.
PAKE (Password-Authenticated Key Exchange)A class of cryptographic protocols (SRP, OPAQUE, SPAKE2, CPace) that let two parties derive a strong shared key from a low-entropy password without exposing the password to offline brute-force or to passive eavesdroppers.
PBKDF2A password-based key derivation function defined in PKCS #5 / RFC 8018 that applies a pseudorandom function with a configurable iteration count and salt.
PEM FormatA textual encoding for cryptographic objects (keys, certificates, CRLs) defined by RFC 7468 that wraps Base64-encoded DER in BEGIN and END header lines.
PepperA server-side secret combined with each password before hashing, held separately from the database to mitigate offline cracking after a hash leak.
Perfect Forward SecrecyA protocol property ensuring that the compromise of long-term keys does not allow decryption of past session traffic.
PIV CardA US federal smart card that carries identity credentials and PKI keys as defined by FIPS 201 and NIST SP 800-73, used by federal employees and contractors.
PKCS#11A standard C API, also called Cryptoki, that lets applications use cryptographic tokens such as hardware security modules and smart cards without depending on a vendor-specific driver.
PKCS#12A password-protected file format (.pfx / .p12) that bundles a private key with its certificate chain, standardised by RFC 7292.
PKCS#7A binary format for packaging signed and/or encrypted data, standardised by the IETF as Cryptographic Message Syntax (CMS) in RFC 5652.
PlaintextReadable, unencrypted form of data that is the input to encryption and the output of correct decryption.
Post-Quantum CryptographyClassical cryptographic algorithms designed to remain secure against attacks by both classical and large-scale quantum computers.
Power Analysis AttackA side-channel attack that recovers secret keys by measuring fluctuations in the power consumption of a cryptographic device during operations.
Private KeyThe secret half of an asymmetric key pair, used to decrypt ciphertext addressed to its owner or to create digital signatures that prove the owner's identity.
Private Set Intersection (PSI)A cryptographic protocol that lets two or more parties compute the intersection of their private sets while learning nothing about the elements that are not in common.
Proxy Re-EncryptionA cryptographic technique that lets a semi-trusted proxy transform a ciphertext encrypted under Alice's key into one decryptable by Bob without learning the plaintext.
Public KeyThe freely distributable half of an asymmetric key pair, used to encrypt messages for its owner or to verify digital signatures produced by the matching private key.
Public-Key CryptographyA branch of cryptography that uses paired public and private keys to enable encryption, key exchange, digital signatures, and authentication without a pre-shared secret.
Quantum CryptographyCryptography that uses quantum-mechanical properties — typically of photons — to achieve security guarantees impossible with classical communication alone.
Quantum Key Distribution (QKD)A method that uses quantum-mechanical properties of photons to let two parties share a secret key while detecting any eavesdropper on the channel.
RFID CloningCopying the identifier or cryptographic data of an RFID tag, such as HID Prox or MIFARE Classic, onto another device to impersonate the original badge.
Ring SignatureA digital signature produced by any one of n public keys without revealing which signer was used, introduced by Rivest, Shamir, and Tauman in 2001.
RSA AlgorithmA public-key algorithm by Rivest, Shamir and Adleman (1977) whose security rests on the difficulty of factoring the product of two large prime numbers.
Salsa20A 256-bit-key stream cipher designed by Daniel J. Bernstein in 2005, selected by the eSTREAM portfolio and the direct ancestor of ChaCha20.
SaltA unique random value combined with a password before hashing to defeat rainbow tables and ensure each user's hash is distinct.
scryptA memory-hard password-based KDF designed by Colin Percival in 2009 and specified in RFC 7914, used for password hashing and for proof-of-work in some cryptocurrencies.
seccompA Linux kernel facility that restricts which system calls a process can make, with the modern seccomp-BPF/eBPF mode enabling fine-grained per-syscall filters.
secp256k1A Koblitz elliptic curve defined by SEC 2, providing ~128-bit security and used by Bitcoin, Ethereum, and many other blockchains for ECDSA and Schnorr signatures.
Secure BootUEFI feature that verifies the cryptographic signature of every boot component, refusing to launch a bootloader, kernel, or driver not signed by a trusted authority.
Secure Multi-Party Computation (MPC)A family of cryptographic protocols that lets several parties jointly compute a function over their private inputs while revealing nothing beyond the output.
SELinuxSecurity-Enhanced Linux, an NSA-developed mandatory access control framework implemented via the Linux Security Module hooks and a type-enforcement policy.
Session KeyA short-lived symmetric key used to protect a single communication session and then discarded.
SHA-1A cryptographic hash function producing a 160-bit digest, designed by the NSA in 1995 and now considered broken for collision resistance.
SHA-256A 256-bit cryptographic hash function from the SHA-2 family, widely used for digital signatures, TLS, blockchains, and integrity verification.
SHA-3A family of hash functions based on the Keccak sponge construction, standardized by NIST as a structurally different alternative to SHA-2.
Shamir's Secret SharingA threshold cryptographic scheme by Adi Shamir (1979) that splits a secret into n shares such that any k can reconstruct it while fewer than k reveal nothing.
Shor's AlgorithmA quantum algorithm that factors large integers and computes discrete logarithms in polynomial time, breaking RSA, Diffie-Hellman, and elliptic-curve cryptography on a sufficiently large quantum computer.
SLH-DSA (FIPS 205)NIST's standardized stateless hash-based post-quantum signature scheme, derived from SPHINCS+ and published as FIPS 205 in August 2024 — the conservative PQ signature option, relying only on hash-function security.
Smart CardA credit-card-sized device with an embedded secure microcontroller that stores credentials and performs cryptographic operations, defined by ISO/IEC 7816 for contact cards.
SPHINCS+A stateless hash-based digital-signature scheme standardized by NIST as FIPS 205 (SLH-DSA) in August 2024, offering conservative post-quantum security with no structured-math assumptions.
Stream CipherA symmetric cipher that encrypts data one bit or byte at a time by XORing it with a pseudorandom keystream derived from a key and nonce.
Symmetric EncryptionAn encryption scheme in which the same secret key is used for both encryption and decryption, offering high speed and strong confidentiality when the key is shared securely.
TEMPEST AttackRecovery of secret information by capturing unintended electromagnetic, acoustic, or optical emanations from electronic equipment.
Threshold CryptographyA class of cryptographic schemes in which a secret key is split across n parties so that any t of them — but no smaller subset — can sign, decrypt, or perform any other key operation.
Triple DES (3DES)A legacy block cipher that applies the DES algorithm three times with two or three keys to extend its key length; now retired by NIST and considered obsolete.
Trusted Platform Module (TPM)Standards-based security chip soldered to a mainboard or implemented in firmware that provides hardware-rooted key storage, attestation, and measured boot.
TwofishA 128-bit-block, 128/192/256-bit-key symmetric cipher designed by Schneier et al. as an AES competition finalist; secure but rarely used because AES became the standard.
XChaCha20-Poly1305An extended-nonce variant of ChaCha20-Poly1305 that uses a 192-bit nonce, making it safe to generate nonces randomly without worrying about collision and well-suited for at-rest encryption and random-nonce designs.
YubiKeyFamily of hardware security keys from Yubico that implement FIDO2, WebAuthn, U2F, PIV smartcard, OpenPGP, and OTP for phishing-resistant authentication.
Zero-Knowledge Proof (ZKP)A cryptographic protocol in which a prover convinces a verifier that a statement is true without revealing anything beyond the validity of the statement itself.
zk-SNARKA Zero-Knowledge Succinct Non-Interactive Argument of Knowledge: a small, fast-to-verify proof that a computation was performed correctly, without revealing its inputs.
zk-STARKA Zero-Knowledge Scalable Transparent Argument of Knowledge: a post-quantum-friendly zero-knowledge proof system that needs no trusted setup and relies only on collision-resistant hash functions.