Hashing Algorithm
Hashing algorithms** are essential tools in cryptography and data security. Unlike encryption, hashing transforms data into a fixed-length string, known as a hash, which cannot be reversed. This chapter explores how hashing works, the most popular algorithms, their real-world applications, and their role in ensuring data integrity and security.
What is a Hashing Algorithm?
A hashing algorithm is a mathematical function that takes input data of any size and returns a fixed-size alphanumeric string called a hash or digest.
Example:
Input:“Hello”SHA-256 Hash:185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969
Hashing is one-way, meaning you cannot reverse the hash back into the original data.
Characteristics of a Good Hash Function
A cryptographic hash function must have these properties:
Deterministic: Same input always produces the same hash.
Fast Computation: Can quickly generate the hash.
Irreversibility: Cannot retrieve original data from hash.
Avalanche Effect: Small changes in input result in drastically different hashes.
Collision Resistance: Two different inputs shouldn’t produce the same hash
How Hashing Works
Input data (text, file, password, etc.)
Pass through a hashing algorithm (like SHA-256)
Get a fixed-length hash string
Store or compare hash without storing actual data
Common Hashing Algorithms
MD5 (Message Digest 5)
Produces 128-bit hash
Fast but not secure anymore (collision-prone)
SHA-1 (Secure Hash Algorithm 1)
Produces 160-bit hash
Now deprecated due to vulnerabilities
SHA-2 Family (SHA-224, SHA-256, SHA-512)
Stronger and widely used in SSL, digital signatures
SHA-3
Newer standard with a different cryptographic structure
Secure and designed as a future-proof solution
Bcrypt / Scrypt / Argon2
Specifically designed for password hashing
Adds salt and slows down brute-force attacks
Use Cases of Hashing
Password storage: Only the hash is stored in databases
Data integrity checks: File or message comparison
Digital signatures: Verifying document authenticity
Blockchain: Securing transaction records
Checksums: Verifying downloaded files
Hashing vs Encryption
| Feature | Hashing | Encryption |
|---|---|---|
| Direction | One-way | Two-way (encrypt/decrypt) |
| Reversible | No | Yes |
| Purpose | Data integrity, verification | Data confidentiality |
| Output size | Fixed-length | Variable length |
Hash Collisions and Security Risks
A hash collision happens when two different inputs produce the same hash. This is rare in strong algorithms but:
MD5 and SHA-1 are known to be vulnerable.
Collisions can be exploited in digital signature forgery and integrity checks.
Salting and Peppering
Salting
Adds a unique random string to input before hashing — prevents precomputed attacks like rainbow tables.
Peppering
A hidden static string added to all inputs — usually kept secret at the application level.
Used heavily in password hashing to improve security.
Limitations of Hashing
Not useful for encrypting confidential data
Cannot reverse or restore original data
Vulnerable to brute-force attacks without salting
Collision attacks possible with weak algorithms
Hashing algorithms are essential for verifying integrity and securing credentials. By understanding and applying strong hash functions (like SHA-256, bcrypt), developers and system architects can significantly improve the safety and integrity of their applications.