MD5 (Message-Digest Algorithm 5) is a widely used cryptographic hash function that creates a 128-bit (32-character hexadecimal) fingerprint for a file or string of any length.
It's like a unique signature that represents the original data.
It was designed by Ronald Rivest in 1991 to replace an earlier algorithm, MD4.
How MD5 Works:
Padding: The input data is padded to ensure its length is a multiple of 512 bits.
Initialization: Four 32-bit variables are initialized with fixed values.
Processing Blocks: The input is processed in 512-bit blocks through four rounds of complex mathematical operations involving bitwise XOR, shifts, and modular additions.
Output: The final 128-bit hash value is generated.
Key Properties:
Deterministic: The same input always produces the same hash.
Irreversible: It's computationally infeasible to reverse the hash to get the original input.
Collision Resistant (in theory): It should be difficult to find two different inputs that produce the same hash.
Common Uses:
File Integrity Verification: Ensure files haven't been tampered with during transmission or storage by comparing their hashes.
Password Storage: Store hashes of passwords instead of plain text for security (though not recommended for password storage anymore due to security vulnerabilities).
Digital Signatures: Verify the authenticity of digital documents.
Security Vulnerabilities:
Collision Attacks: Researchers have found ways to create two different inputs that produce the same MD5 hash, compromising its collision resistance.
Pre-Image Attacks: Potential for attacks to find a partial input that matches a given hash.
Recommendations:
Not suitable for password storage or security guarantees.
Prefer SHA-256 or SHA-3 for stronger security.
Use MD5 only for non-critical applications like file integrity checks.