Cryptographic Hash Glossary

This glossary defines common terms encountered when working with hash functions and cryptography. Understanding this terminology helps you navigate technical documentation, security discussions, and our user guide. Terms are listed alphabetically for easy reference.

Algorithm
A step-by-step procedure for calculations. Hash algorithms like SHA-256 define the exact mathematical operations that transform input into hash output.
Avalanche Effect
A property of good hash functions where changing a single bit of input changes approximately half the bits in the output. This ensures similar inputs produce very different hashes.
Bit
The smallest unit of digital information, representing 0 or 1. Hash output sizes are typically measured in bits (e.g., SHA-256 produces 256 bits).
Block Cipher
An encryption algorithm that operates on fixed-size blocks of data. Some hash functions use block cipher construction internally.
Checksum
A value computed from data to verify integrity. While checksums can use simple algorithms, cryptographic hashes provide stronger protection.
Collision
When two different inputs produce the same hash output. Secure hash functions make finding collisions computationally infeasible.
Collision Resistance
The property that it is computationally infeasible to find two different inputs that produce the same hash output.
Cryptographic Hash Function
A hash function designed to be secure against attacks. Properties include collision resistance, preimage resistance, and avalanche effect.
Deterministic
The property that the same input always produces the same output. Hash functions are deterministic, enabling verification.
Digest
Another name for a hash value or hash output. The term suggests the hash digests or summarizes the input data.
Encryption
The process of encoding information so only authorized parties can read it. Unlike hashing, encryption is reversible with the correct key.
Fingerprint
A colloquial term for a hash value, emphasizing its role as a unique identifier for data.
Hash Function
A mathematical function that converts input of any size into fixed-size output. Cryptographic hash functions add security properties.
Hash Rate
In cryptocurrency mining, the speed at which hash computations are performed, typically measured in hashes per second.
Hash Value
The output of a hash function. For SHA-256, this is a 256-bit (64 hexadecimal character) string.
Hexadecimal
A base-16 numbering system using digits 0-9 and letters a-f. Hash values are commonly displayed in hexadecimal format.
HMAC
Hash-based Message Authentication Code. A construction that combines a hash function with a secret key to provide both integrity and authentication.
Integrity
The property that data has not been modified. Hash verification demonstrates data integrity.
MD5
Message Digest Algorithm 5. A 128-bit hash function that is fast but broken for security purposes due to discovered collision vulnerabilities.
Merkle Tree
A tree structure where each node is the hash of its children. Used in blockchain and distributed systems for efficient verification.
Message Authentication
Verification that a message came from the claimed sender and was not modified. HMAC provides message authentication.
NIST
National Institute of Standards and Technology. The US agency that standardizes cryptographic algorithms including SHA-2.
One-Way Function
A function easy to compute in one direction but infeasible to reverse. Hash functions are one-way.
Preimage
The input that produces a specific hash output. Finding the preimage from just the hash should be infeasible.
Preimage Resistance
The property that given a hash output, it is computationally infeasible to find any input that produces that output.
Rainbow Table
A precomputed table for reversing hash functions, typically used to crack passwords. Salting defeats rainbow tables.
Salt
Random data added to input before hashing. Salts ensure identical inputs produce different hashes, preventing rainbow table attacks.
SHA-1
Secure Hash Algorithm 1. A 160-bit hash function that is deprecated for security due to demonstrated collision attacks.
SHA-2
A family of hash functions including SHA-224, SHA-256, SHA-384, and SHA-512. Currently the standard for security applications.
SHA-256
A 256-bit hash function from the SHA-2 family. Widely used and considered secure for virtually all applications.
SHA-3
The newest hash standard using the Keccak algorithm. Provides an alternative to SHA-2 with different internal construction.
SHA-384
A 384-bit hash function from the SHA-2 family. Provides additional security margin over SHA-256.
SHA-512
A 512-bit hash function from the SHA-2 family. The strongest variant, producing 128 hexadecimal characters.
UTF-8
A character encoding standard that represents text as bytes. Hash functions operate on bytes, so encoding affects output.
Work Factor
In password hashing, an intentional computational cost that slows attack attempts. bcrypt and similar algorithms use configurable work factors.

Additional Resources

For more in-depth explanations, explore these resources: