Online Hash Calculator - SHA-256, SHA-512, SHA-1

What is a Hash Function?

A cryptographic hash function takes input of any size and produces a fixed-size output (the hash or digest). Hash functions are one-way—you cannot reverse the hash to get the original input. This makes them essential for password storage, data integrity, and digital signatures.

Hash Algorithms Compared

• SHA-1: 160-bit output. Deprecated due to vulnerabilities.
• SHA-256: 256-bit output. Most widely used secure hash.
• SHA-384: 384-bit output. Truncated version of SHA-512.
• SHA-512: 512-bit output. Highest security, longer hash.

Common Use Cases

• File Integrity: Verify downloads haven't been tampered with.
• Password Storage: Store hashes, not plain passwords.
• Digital Signatures: Sign hash of document, not full content.
• Blockchain: SHA-256 secures Bitcoin transactions.
• Git: Commit hashes identify code versions.

Hash Properties

• Deterministic: Same input always produces same hash.
• Fast: Hashes compute quickly for any input size.
• Irreversible: Cannot derive input from hash.
• Unique: Different inputs produce different hashes (ideally).
• Avalanche: Small input changes cause large hash changes.

Security Recommendations

• Use SHA-256 or SHA-512 for new applications.
• Avoid MD5 and SHA-1 for security purposes.
• For passwords, use bcrypt, Argon2, or PBKDF2.
• Always salt passwords before hashing.