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RSA Asymmetric Cryptography

Generate RSA key pairs, encrypt/decrypt with RSA-OAEP, sign and verify with RSASSA-PKCS1-v1_5. All operations in-browser via Web Crypto API.

1. Key Pair

Key Size:

Public Key (PEM):

Not generated

Private Key (PEM):

Not generated

2. Encryption / Decryption (RSA-OAEP with SHA-256)

Message:

Output (Base64):

RSA-OAEP has a message size limit: keySize/8 - 42 bytes (e.g. 190 bytes for 2048-bit). For larger data, use hybrid encryption.

3. Sign / Verify (RSASSA-PKCS1-v1_5 with SHA-256)

Message to sign:

Signature (Base64):

Verification Result:

Uses Web Crypto API with RSA-OAEP (SHA-256) for encryption and RSASSA-PKCS1-v1_5 (SHA-256) for signatures. Keys are generated in-browser and never leave your device. PEM export uses PKCS#8 (private) and SPKI (public) format.

How to Use

Encryption: Generate a key pair, enter your message, click "Encrypt with Public Key". Share the Base64 ciphertext and the private key holder can decrypt it.

Decryption: Paste the Base64 ciphertext, ensure the corresponding private key is loaded, click "Decrypt with Private Key".

Signing: Enter a message, click "Sign with Private Key" to produce a Base64 signature. Anyone with the public key can verify the signature was produced by the private key holder.

Key export: Use the Copy buttons to export public/private keys in PEM format for use in other systems (OpenSSL, Java, Python).

Example Use Cases

Key exchange — Encrypt a symmetric key with the recipient's RSA public key
Digital signatures — Sign documents to prove authenticity and integrity
Certificate testing — Generate test key pairs for TLS/mTLS development
JWT signing — Test RS256 JWT signatures with generated keys