RSA Sign/Verify
Sign and verify messages with RSA (SHA-256) using PEM keys
Uses Web Crypto RSASSA-PKCS1-v1_5 with SHA-256. Private keys never leave your browser.
About RSA Sign/Verify
Sign messages with an RSA private key and verify signatures with the corresponding public key, all in your browser. RSA digital signatures provide authentication and non-repudiation — proving that a message was created by the holder of a specific private key and was not altered in transit. This tool accepts PEM-encoded keys (PKCS#8 for private, SPKI for public) and uses the Web Crypto API for all operations. Your private keys and messages never leave your device.
How to Use RSA Sign/Verify
- Paste your PEM-encoded private key to sign, or public key to verify.
- Enter the message you want to sign or verify.
- Click Sign to generate a signature, or paste a signature and click Verify.
- Copy the signature output using the copy button.
RSA Sign/Verify FAQ
Which key formats are supported?
Private keys should be in PKCS#8 PEM format and public keys in SPKI PEM format. These are the standard formats used by OpenSSL and most cryptographic libraries.
Can this encrypt data with RSA?
No. This tool focuses specifically on RSA digital signatures (sign and verify). For encryption, use the AES-GCM tool.
Which signature algorithm is used?
The tool uses RSASSA-PKCS1-v1_5 with SHA-256 via the Web Crypto API, which is widely compatible with most systems.
Is my private key sent to a server?
No. All signing and verification happens locally in your browser via the Web Crypto API. Your private key never leaves your device.
What are RSA signatures used for?
RSA signatures verify document authenticity, authenticate API requests, sign software releases and packages, validate JWT tokens, and prove message origin in secure communications.