JSON to Java
Generate Java DTOs and review validation-oriented API models.
Hash / HMAC
Run digest and HMAC computations over UTF-8 text or hex/base64 binary input. Ideal for file checksums, verifying server signatures, and producing test data. Output is copyable as hex or base64.
HMAC is not simply `hash(key + message)`. It pads the key, XORs it with ipad and opad, and hashes twice. A mismatched encoding between client and server is the most common cause of signature mismatch.
Three usual culprits: (1) the key should be raw UTF-8 but was pasted as base64, (2) newline style (`\n` vs `\r\n`) differs in the message, (3) output is compared as hex while the server returns base64. This tool lets you flip each encoding independently to spot the mismatch.
AWS Signature v4 style
HMAC-SHA-256, key: derived signing key, message: canonical request, output: hex
GitHub webhook
HMAC-SHA-256, key: repo secret, message: raw body, output: 'sha256=' + hex
File integrity
SHA-256 digest, input: UTF-8 text or file bytes, output: hex
Q. Can I use MD5 to hash passwords? No. Use bcrypt, argon2, or scrypt — memory-hard algorithms built for the purpose.
Q. Are SHA-256 and HMAC-SHA-256 the same? No. SHA-256 summarises data without a key. HMAC pairs a shared key with the data to prevent forgery.
Q. Can I hash binary files? Today only hex or base64 pasted input is supported; direct file upload is not.
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