Hash
Definition
A fixed-length string of characters generated from input data by a hash function, used for data integrity verification, password storage, and digital signatures.
A hash function takes input data of any size and produces a fixed-length output string called a hash, digest, or checksum. Good hash functions are deterministic (same input always produces same output), fast to compute, irreversible (cannot reconstruct input from hash), and collision-resistant (different inputs produce different hashes).
Common hash algorithms include SHA-256 (used in Bitcoin and digital certificates), SHA-3, bcrypt and Argon2 (designed for password hashing with built-in salting and adjustable work factors), and MD5 (now considered insecure but still used for checksums).
Hashing has numerous applications: verifying file integrity (checksums), storing passwords securely (never store plaintext passwords), data structures (hash tables), digital signatures, blockchain technology, and de-duplication. Unlike encryption, hashing is a one-way process and cannot be reversed to recover the original data.
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Related Terms
Encryption
techThe process of converting readable data (plaintext) into an unreadable format (ciphertext) using an algorithm and key, protecting it from unauthorized access.
SSL/TLS (Secure Sockets Layer / Transport Layer Security)
techCryptographic protocols that provide secure communication over computer networks, encrypting data between a web server and browser.
Base64
techA binary-to-text encoding scheme that converts binary data into a string of ASCII characters, commonly used for embedding data in web pages and emails.
JWT (JSON Web Token)
techA compact, URL-safe token format used for securely transmitting information between parties as a JSON object, commonly used for authentication.
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