BRev SHA-512 hash generator
SHA-512 produces a 512-bit digest — 128 hexadecimal characters — and belongs to the same SHA-2 family as SHA-256. It uses 64-bit words and a 1024-bit block rather than SHA-256’s 32-bit words and 512-bit block, which has a counter-intuitive consequence: on 64-bit hardware SHA-512 is frequently faster than SHA-256 for large inputs, because each round processes twice as much data.
Whether the longer digest buys security is a different question. SHA-256 already has no practical attack, and 128 bits of collision resistance is far beyond anything reachable — doubling it does not change any real threat model today. The genuine reasons to choose SHA-512 are performance on 64-bit systems, a requirement in a specification you must comply with, and length extension: SHA-512/256, a truncated variant, resists length-extension attacks that plain SHA-256 does not.
The cost is practical rather than cryptographic. A 128-character digest does not fit neatly in a fixed-width database column sized for SHA-256, is unwieldy in a URL or a filename, and is harder for a human to compare by eye. That is precisely why SHA-512/256 exists — SHA-512’s internals with a 256-bit output — and why most projects publish SHA-256 for release checksums.
SHA-512 in numbers
| Property | Value |
|---|---|
| Output | 512 bits — 128 hex characters |
| Block size | 1024 bits, 64-bit words |
| Published | 2001 (NSA/NIST), FIPS 180-2 — SHA-2 family |
| Collision resistance | No practical attack known; 256-bit collision strength |
| Performance | Often faster than SHA-256 on 64-bit CPUs for large inputs |
Is SHA-512 safe to use — and for what?
“Broken” and “fine” are both true of most hash functions depending on the job, so the answer is per use, not per algorithm.
| Use | Verdict | Why |
|---|---|---|
| Large-file hashing on 64-bit systems | Yes | The 64-bit word size makes it measurably faster than SHA-256 on big inputs, so there is no throughput reason to avoid it. |
| Compliance with a specification that names it | Yes | Some standards and government profiles require SHA-384 or SHA-512. Follow the specification — the choice has been made for you. |
| Where length-extension resistance matters | Yes | Use SHA-512/256, the truncated variant, which resists length-extension attacks that plain SHA-256 and SHA-512 are vulnerable to. HMAC also removes the problem for keyed use. |
| Release checksums for public download | Yes | Works fine, but SHA-256 is what most tooling and instructions expect, and a 128-character string is harder to compare by eye. Publishing both is common. |
| Password storage | No | No better than SHA-256 for this. Being fast is the disqualifying property, and extra digest length does not slow an attacker down. Use Argon2, scrypt or bcrypt. |
FAQ
Is SHA-512 more secure than SHA-256?
It has a larger digest, but SHA-256 has no practical attack, so the extra length does not address any current threat. Choose SHA-512 for 64-bit performance or because a specification requires it — not for a security upgrade.
Why is SHA-512 sometimes faster than SHA-256?
It operates on 64-bit words and 1024-bit blocks, so each round processes twice as much data. On 64-bit CPUs that outweighs the extra work per round for large inputs — though hardware SHA-256 acceleration can flip the result.
What is SHA-512/256?
SHA-512’s internals with a different initial state, truncated to 256 bits. It gives SHA-512’s 64-bit performance with a manageable digest length, and it resists length-extension attacks that the untruncated variants do not.