Question 1

What is a cryptographic hash?

Accepted Answer

A cryptographic hash function takes any input and produces a fixed-length digest. The same input always produces the same digest, but even a single character change produces a completely different one. Hashes are one-way — you cannot recover the original input from the digest. They are used for data integrity checks, password storage (salted), digital signatures, and file verification.

Question 2

Which algorithm should I use?

Accepted Answer

SHA-256 is the current default recommendation for most purposes — it is secure, widely supported, and used by TLS, Bitcoin, and most modern software. SHA-512 provides a larger output and is preferred when maximum security margin is required. SHA-1 and MD5 are cryptographically broken and should only be used for non-security purposes such as legacy checksums or cache keys.

Question 3

Why is MD5 considered insecure?

Accepted Answer

MD5 is vulnerable to collision attacks — it is possible to craft two different inputs that produce the same MD5 digest. This makes it unsuitable for security-sensitive uses such as digital signatures or password storage. It remains useful for non-security tasks like checksumming files for accidental corruption or generating cache keys.

Question 4

Is my text sent to a server?

Accepted Answer

No. SHA-1, SHA-256, SHA-384, and SHA-512 are computed using the browser's built-in Web Crypto API (crypto.subtle.digest). MD5 is computed with a pure JavaScript implementation in the page. Nothing you type is ever transmitted to any server.

Hash Generator — MD5, SHA-1, SHA-256, SHA-512

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