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What Is a Cryptographic Hash?
A cryptographic hash function takes any input of any length and produces a fixed-length output called a hash, digest, or checksum. The output is always the same length regardless of whether the input is one character or one gigabyte. SHA-256 always produces a 256-bit (64 hexadecimal character) output. SHA-512 always produces a 512-bit (128 hexadecimal character) output.
Cryptographic hash functions have three core properties. They are deterministic: the same input always produces the same output. They are one-way: given a hash, it is computationally infeasible to find the original input. They are collision-resistant: it is computationally infeasible to find two different inputs that produce the same hash output.
Hashes are used throughout software and security: verifying file integrity (checksums), storing passwords securely (with salting and key stretching), generating digital signatures, creating unique identifiers for content, and building data structures like hash tables and Merkle trees. If you download a file and the provider publishes its SHA-256 hash, you can verify you received the correct file by hashing the download and comparing the output.
- File integrity verification: hash a downloaded file and compare against the publisher checksum
- Password storage: hash passwords with a salt before storing (use bcrypt or Argon2, not raw SHA)
- Digital signatures: sign the hash of a document rather than the document itself
- Content-based identifiers: hash file content to detect duplicates or changes
- HMAC authentication: use a shared secret to create a keyed hash for API request verification
SHA-256 vs SHA-512 — Which Algorithm to Use?
SHA-256 and SHA-512 are both part of the SHA-2 (Secure Hash Algorithm 2) family, standardized by NIST in 2001. SHA-256 produces a 256-bit hash and is the most widely used algorithm for security applications. It is used in TLS/HTTPS certificates, Bitcoin proof-of-work, JWT signatures (when using HS256 or RS256), and most modern checksum verification tools. SHA-256 is the default recommendation for most security use cases in 2024 and beyond.
SHA-512 produces a 512-bit hash and is marginally harder to brute-force than SHA-256. On 64-bit processors, SHA-512 is often faster than SHA-256 because the SHA-512 algorithm is designed to operate on 64-bit words, which 64-bit CPUs handle natively. SHA-384 is a truncated variant of SHA-512 that produces 384 bits. If you need longer hashes or work primarily on 64-bit servers, SHA-512 or SHA-384 can be a good choice.
SHA-1 produces a 160-bit hash and is included here for legacy use cases such as verifying old checksums, computing Git object hashes, and working with older certificate fingerprints. SHA-1 is cryptographically broken for security purposes — collision attacks have been demonstrated since 2017. Do not use SHA-1 for new security applications such as password hashing, digital signatures, or HMAC keys.
Why MD5 Is Not Included
MD5 (Message Digest Algorithm 5) is not included because it is cryptographically broken. MD5 collision attacks — where two different inputs produce the same hash output — have been demonstrated in practice since 2004. In 2008, researchers used MD5 collisions to forge a legitimate-looking SSL certificate, demonstrating that the vulnerability was exploitable in real-world attacks.
MD5 should not be used for any security purpose: not for password hashing, not for digital signatures, not for verifying security-critical files. Its collision resistance is completely broken. For any security application, use SHA-256 or SHA-512 instead. The only remaining legitimate use for MD5 is non-security checksums where collision resistance is not required, such as verifying file integrity in a trusted environment where deliberate tampering is not a concern.
If you need to compute an MD5 hash for a legacy system, tool, or protocol that specifically requires it and collision resistance is not a concern, use a dedicated MD5 tool. This hash generator focuses on the modern secure hash algorithms recommended by NIST and used in current security standards.
Why marketers use this tool
- Generate SHA-1, SHA-256, SHA-384, and SHA-512 hashes using your browser Web Crypto API
- Hash any text instantly — messages, tokens, file content snippets, or API keys
- Fully client-side — your input never leaves your browser or device
Frequently Asked Questions
What is the difference between SHA-256 and SHA-512?
SHA-256 produces a 256-bit (64 hexadecimal character) hash. SHA-512 produces a 512-bit (128 hexadecimal character) hash. Both are part of the SHA-2 family and are considered secure. SHA-256 is more widely supported and is the default in most security tools and protocols including TLS, Bitcoin, and JWT. SHA-512 can be faster on 64-bit hardware and produces a longer, marginally harder-to-brute-force output. For most applications, SHA-256 is the correct choice.
Can I reverse a SHA-256 hash back to the original text?
No. SHA-256 is a one-way function. There is no mathematical operation that reverses the hash back to the input. The only practical way to find the input for a given hash is to try candidate inputs, hash each one, and check whether the output matches — which is called a brute-force attack. For short or predictable inputs like common passwords, precomputed rainbow tables make this feasible. For long, random inputs, brute-force is computationally infeasible.
Is SHA-1 still safe to use?
SHA-1 is no longer safe for security-critical applications. Collision attacks against SHA-1 were demonstrated practically in 2017 (the SHAttered attack) and the algorithm has been officially deprecated by NIST. Modern browsers no longer accept SHA-1 in TLS certificates. SHA-1 is still used for non-security purposes such as computing Git object hashes, but it should not be used for new digital signatures, certificate fingerprints, HMAC keys, or password hashing.
Should I use SHA-256 or bcrypt for password hashing?
Neither raw SHA-256 nor raw SHA-512 should be used directly for password hashing. These algorithms are fast by design, which makes them vulnerable to brute-force attacks when used for passwords. Password hashing requires an algorithm that is deliberately slow and memory-intensive. Use bcrypt, scrypt, or Argon2id for password storage. These algorithms include a built-in salt, are configurable in terms of computational cost, and are designed specifically to resist GPU-based brute-force attacks.
What is a hash collision?
A hash collision occurs when two different inputs produce the same hash output. Because hash functions map inputs of any length to a fixed-length output, collisions must theoretically exist — there are infinitely many possible inputs but only a finite number of possible outputs. A secure hash function makes finding collisions computationally infeasible. SHA-256 has never had a collision demonstrated in practice. The theoretical collision resistance of SHA-256 is 2^128 operations — far beyond what any computer can perform.