What is SHA-256?
A cryptographic hash function that produces a 256-bit (32-byte) hash value. Part of the SHA-2 family, it's widely used for data integrity verification, digital signatures, password hashing, and as the backbone of Bitcoin's proof-of-work.
Also known as: SHA256, Secure Hash Algorithm 256
SHA-256 is the workhorse of modern cryptography. It takes any input and produces a 64-character hexadecimal string that's practically unique to that input.
Example
Input: "Hello"
SHA-256: 185f8db32271fe25f561a6fc938b2e264306ec304eda518007d1764826381969
Input: "hello" (lowercase)
SHA-256: 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824
One capital letter = completely different hash.
Technical Properties
- Output: Always 256 bits (64 hex characters)
- Speed: ~500 MB/s on modern CPUs
- Security: 2^128 operations to break (infeasible)
- Collision resistance: No known collisions
Where It's Used
Blockchain & Cryptocurrency
- Bitcoin mining (double SHA-256)
- Transaction verification
- Block hashing
SSL/TLS Certificates
- Certificate signing
- Connection verification
Password Hashing
- Often with PBKDF2, bcrypt, or Argon2
- Salt + multiple rounds for security
File Verification
- Software downloads
- Package managers (npm, pip)
- Git commits
Digital Signatures
- Document signing
- Code signing
SHA-256 vs Other Hash Functions
| Function | Bits | Speed | Security |
|---|---|---|---|
| MD5 | 128 | Fast | Broken |
| SHA-1 | 160 | Fast | Weak |
| SHA-256 | 256 | Medium | Strong |
| SHA-512 | 512 | Faster on 64-bit | Strong |
| SHA-3 | Variable | Slower | Strong |
Security Considerations
- Don't use alone for passwords: Add salt and key stretching
- Quantum threat: Eventually vulnerable to quantum computers
- Not encryption: Can't recover original data from hash
Related Terms
Encryption
The process of converting information into a code to prevent unauthorized access. Encryption transforms readable data (plaintext) into an unreadable format (ciphertext) using a cryptographic algorithm and key. Only those with the correct key can decrypt and read the original data.
Hash Function
A mathematical function that converts any input data into a fixed-size string of characters (hash). Cryptographic hash functions are one-way, meaning you cannot reverse the process to recover the original data.
Have more questions?
Use our guided flow to get the right next privacy step for SHA-256.
Open Guided Flow