Rsa Sign Verify

In public-key cryptography (like RSA), you have two keys: a Public Key (shared with the world) and a Private Key (kept secret). Most people associate RSA with encryption, but it is equally important for Authentication.

• Encryption: Someone uses your Public Key to lock a message. Only you can unlock it with your Private Key. This provides confidentiality.
• Signing: You use your Private Key to "lock" (sign) a message. Anyone in the world can "unlock" (verify) it using your Public Key. This provides authenticity.

Because RSA operations are mathematically slow and have strict size limits, we rarely sign the entire message directly. Instead, the process works like this:

1. The computer hashes the original message using an algorithm like SHA-256.
2. The computer encrypts that small, fixed-length hash using your Private Key. This encrypted hash is the "Signature".
3. To verify it, the receiver decrypts the signature using your Public Key to get the hash. They then hash the message themselves. If the two hashes match perfectly, it guarantees that (a) you wrote the message, and (b) nobody altered it in transit.

When creating a signature, Web Crypto offers two main RSA padding schemes:

• RSASSA-PKCS1-v1_5: The older, extremely common standard (this is what JSON Web Tokens use for the RS256 algorithm).
• RSA-PSS (Probabilistic Signature Scheme): A newer, more robust standard that introduces randomness into the signature process, meaning signing the same message twice yields different signatures (yet both remain mathematically valid).