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[CHOOSING THE RIGHT HASH ALGORITHM]

A comprehensive comparison of MD5, SHA-1, SHA-256, SHA-384, SHA-512, and BLAKE2b—with clear recommendations for every use case.

By Vladimir Lorentz | Last updated: January 2025 | ~7 min read

[QUICK ANSWER]

For most users: Use SHA-256. It's secure, widely supported, and the industry standard for file verification.

For matching existing checksums: Use whatever algorithm the publisher provides (often MD5, SHA-1, or SHA-256).

For maximum speed with security: Use BLAKE2b. It's faster than SHA-256 while equally secure.

Keep reading for detailed comparisons and specific recommendations.

[ALGORITHM COMPARISON TABLE]

Algorithm Output Size Security Speed Recommended Use
MD5 128 bits (32 chars) Broken Very Fast Legacy, duplicates only
SHA-1 160 bits (40 chars) Broken Fast Legacy compatibility only
SHA-256 256 bits (64 chars) Secure Medium General purpose (recommended)
SHA-384 384 bits (96 chars) Secure Medium Compliance requirements
SHA-512 512 bits (128 chars) Very Secure Medium* Maximum security margin
BLAKE2b 512 bits (128 chars) Secure Very Fast Performance + security

*SHA-512 can be faster than SHA-256 on 64-bit systems due to how the algorithm operates on 64-bit words.

[MD5: THE LEGACY OPTION]

MD5 (Message Digest 5) was designed in 1991 and produces a 128-bit hash. It was once the standard for file verification, but MD5 is now cryptographically broken.

The Problem with MD5

In 2004, researchers demonstrated practical collision attacks against MD5. This means attackers can create two different files with the same MD5 hash. In 2012, the Flame malware exploited an MD5 collision to forge Windows Update certificates. MD5 should never be used for security purposes.

When MD5 is Still Acceptable

  • • Detecting accidental corruption (not malicious modification)
  • • Finding duplicate files
  • • Verifying downloads when only MD5 is provided and you trust the source completely
  • • Legacy system compatibility

RECOMMENDATION:

Avoid MD5 for security purposes. If a publisher only provides MD5 checksums, ask them to also provide SHA-256. For new projects, never choose MD5.

[SHA-1: DEPRECATED BUT LINGERING]

SHA-1 (Secure Hash Algorithm 1) produces a 160-bit hash. It was the U.S. government standard from 1995 until 2010. Like MD5, SHA-1 is now broken.

The Fall of SHA-1

In 2017, Google and CWI Amsterdam announced "SHAttered"—the first practical SHA-1 collision attack. They created two different PDF documents with identical SHA-1 hashes. Major browsers stopped trusting SHA-1 certificates, and most security standards now prohibit its use.

When You Might Encounter SHA-1

  • • Git uses SHA-1 for commit hashes (though git is migrating to SHA-256)
  • • Older software still providing SHA-1 checksums
  • • Legacy systems and embedded devices

RECOMMENDATION:

Only use SHA-1 when required for compatibility. Always prefer SHA-256 or stronger when you have a choice.

[SHA-256: THE RECOMMENDED STANDARD]

SHA-256 is part of the SHA-2 family, designed by the NSA and published in 2001. It produces a 256-bit (64-character) hash and is currently considered secure with no known practical attacks.

Why SHA-256 is the Default Choice

  • ✓ Widely supported: Every major platform, library, and tool supports SHA-256
  • ✓ Industry standard: Used in TLS/SSL, Bitcoin, code signing, and federal standards
  • ✓ Balanced: Good security margin without excessively long hash strings
  • ✓ Well-analyzed: Decades of cryptographic scrutiny with no significant weaknesses found

Use SHA-256 When:

  • • Verifying software downloads
  • • Creating audit trails and compliance documentation
  • • Storing password hashes (with proper salting)
  • • Any security-sensitive file verification
  • • When you're unsure which algorithm to use

RECOMMENDATION:

SHA-256 is the safe default for virtually all file hashing needs. Unless you have specific requirements for something else, use SHA-256.

[SHA-384 & SHA-512: EXTRA SECURITY MARGIN]

SHA-384 and SHA-512 are also part of the SHA-2 family. They produce 384-bit and 512-bit hashes respectively, offering larger security margins than SHA-256.

SHA-384

SHA-384 is essentially SHA-512 truncated to 384 bits. It exists primarily for government and compliance requirements that specify a 192-bit security level. If you're not bound by such requirements, SHA-256 or SHA-512 are usually better choices.

SHA-512

SHA-512 produces a 512-bit hash—the longest hash strings (128 hexadecimal characters). Interestingly, SHA-512 can be faster than SHA-256 on 64-bit processors because it operates on 64-bit words rather than 32-bit words.

When to Use SHA-512:

  • • Maximum future-proofing against theoretical attacks
  • • Security-critical applications where the extra hash length isn't a problem
  • • When you want potentially better performance on 64-bit systems
  • • Some publishers prefer SHA-512 (e.g., Apache Software Foundation)

NOTE:

In practical terms, SHA-256's 256-bit output already provides more security than we can reasonably ever need (2^128 operations to find a collision). SHA-512's extra length is a "belt and suspenders" approach rather than a necessity.

[BLAKE2B: THE MODERN ALTERNATIVE]

BLAKE2b is a cryptographic hash function designed in 2012 as an improved version of BLAKE (a SHA-3 finalist). It's specifically optimized for 64-bit platforms and offers outstanding performance while maintaining high security.

Why BLAKE2b is Special

  • ⚡ Faster than MD5: BLAKE2b outperforms MD5 while being cryptographically secure
  • ⚡ As secure as SHA-3: Based on the same design principles, thoroughly analyzed
  • ⚡ Simpler implementation: Less prone to implementation errors than SHA-2
  • ⚡ Widely adopted: Used in Argon2 (password hashing winner), WireGuard, and many modern systems

Use BLAKE2b When:

  • • Hashing large files where speed matters
  • • Building new systems without legacy constraints
  • • You want modern security with maximum performance

Considerations:

  • • Less commonly published by software vendors than SHA-256
  • • Not approved for U.S. government use (SHA-2 and SHA-3 are)

RECOMMENDATION:

BLAKE2b is an excellent choice for personal use, especially when hashing many or large files. For verification against published checksums, you'll usually need SHA-256 to match what publishers provide.

[DECISION GUIDE]

Use this flowchart to choose the right algorithm:

Q: Are you verifying against an existing checksum?

→ YES: Use the same algorithm as the published checksum

→ NO: Continue below

Q: Is this for security-critical purposes?

→ YES: Use SHA-256 (or SHA-512 for maximum margin)

→ NO: Continue below

Q: Do you need compatibility with legacy systems?

→ YES: Use MD5 or SHA-1 only if absolutely required

→ NO: Continue below

Q: Is performance a priority (large files, many files)?

→ YES: Use BLAKE2b

→ NO: Use SHA-256 (safe default)

[FUTURE-PROOFING YOUR CHOICE]

Cryptographic algorithms can become vulnerable over time as computing power increases and new attack techniques are discovered. Here's what we know about the future:

  • ›
    SHA-256 and SHA-512 are expected to remain secure for decades. No practical attacks are on the horizon.
  • ›
    BLAKE2b is also expected to remain secure, with similar or better security properties to SHA-2.
  • ›
    Quantum computing threatens all current hash algorithms theoretically, but practical quantum computers capable of breaking SHA-256 are likely decades away. When they arrive, we'll need entirely new algorithms.
  • ›
    SHA-3 exists as a backup if SHA-2 is ever compromised. It uses a completely different design (Keccak), so an attack on SHA-2 wouldn't affect SHA-3.

For now, SHA-256 and BLAKE2b are safe choices. Keep your tools updated and follow security news for any cryptographic developments.

[TRY DIFFERENT ALGORITHMS]

Experiment with different hash algorithms on Hash File Online. Hash the same file with different algorithms to see the output differences and compare speeds.

[START HASHING]

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