Question 1

What is SHA-256?

Accepted Answer

SHA-256 is a cryptographic hash function from the SHA-2 family, published by NIST in 2001 (FIPS 180-4). It produces a 256-bit (32-byte) digest from input of any length, typically displayed as 64 hexadecimal characters. SHA-256 is the modern default for general-purpose cryptographic hashing — used in Bitcoin's proof-of-work, TLS certificates, code signing, Linux package manager checksums, and Git's object hashes (until Git 2.42+ which can use SHA-256 instead of SHA-1). No practical collision attacks exist against SHA-256 in 2026. The full keyspace (2^256) is well beyond brute-force reach even by national-level adversaries.

Question 2

Is SHA-256 suitable for password hashing?

Accepted Answer

No — even though it's cryptographically strong, SHA-256 is too FAST for password storage. A modern GPU computes ~25 billion SHA-256 hashes per second. That means a 10-character random password could be brute-forced in days. Password hashes need slowness, not speed. Use Argon2id (OWASP first choice) or bcrypt (acceptable alternative) for storing user passwords. SHA-256 is fine for: file integrity, signature verification, Merkle trees, content-addressed storage, derive-once material that's then run through a slow KDF.

Question 3

How does this compare to SHA-512?

Accepted Answer

SHA-512 produces a 512-bit digest (128 hex chars) — twice the length of SHA-256. On 64-bit CPUs, SHA-512 can be slightly faster than SHA-256 because it operates on 64-bit words natively. The security difference is mostly theoretical — both have collision resistance of ~2^(n/2), so SHA-256 has 2^128 collision resistance, SHA-512 has 2^256. Both are well beyond practical attacks. Use SHA-256 when interoperability with the most systems matters (Bitcoin, TLS, code signing all use SHA-256). Use SHA-512 when you specifically need 256+ bits of collision resistance or you're on a 64-bit-optimized platform.

Question 4

Why use the Web Crypto API?

Accepted Answer

crypto.subtle.digest() is the browser's native implementation, available in every modern browser. It's faster than any pure-JS library because it uses optimized native code (sometimes CPU SHA-NI instructions on modern hardware). It also runs off the main thread, so hashing a large file doesn't freeze the UI. This tool uses crypto.subtle.digest directly with no wrapper library — the JavaScript code that runs in your browser is approximately 20 lines.

SHA-256 Generator

Where SHA-256 Is Used

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