Hash Generator

A hash function takes input data of any size and produces a fixed-length output called a hash or digest. The same input always produces the same output, but tiny input changes produce completely different hashes. Hashes are one-way — you cannot reconstruct the input from the hash alone.

MD5 is no longer considered cryptographically secure for security-critical applications. Researchers have found collision attacks (two different inputs producing the same MD5 hash). MD5 is still useful for checksums and data integrity verification where security is not the primary concern. For passwords and signatures, use SHA-256 or SHA-512.

SHA-256 is used extensively in security-critical systems. It is part of TLS/SSL certificate chains, Bitcoin's proof-of-work algorithm, code-signing, and password storage (with salting). SHA-256 produces a 256-bit (64 hex character) digest and is considered secure for modern use.

HMAC (Hash-based Message Authentication Code) combines a secret key with a hash function to produce a message authentication code. It verifies both data integrity and authenticity — only someone with the secret key can produce the correct HMAC. HMAC-SHA-256 is commonly used in API authentication and JWT signatures.

No — hash functions are designed to be one-way. There is no mathematical way to compute the original input from a hash. However, weak or common inputs can be found via rainbow tables (precomputed hash databases). This is why passwords should always be salted before hashing.