Sign and verify data or messages using RSA cryptography.

Optionally exchange signed data via QR codes.

Usage

1. create and store an RSA keypair (default key length 1024 bits)
2. sign a message using the private key, store the signature (binary data, SHA-256 hash)
3. verify the message using the public key and signature

python QRSA.py create --out priv.key --pubout pub.key
python QRSA.py sign   --message "Joost K;2021-01-22;My Company" --key priv.key --out signature.bin
python QRSA.py verify --message "Joost K;2021-01-22;My Company" --key pub.key --sig signature.bin

SHA-256

If one changes the message (or signature), verification fails:

python QRSA.py verify --message "Joost K;2021-01-23;My Company" --key pub.key --sig signature.bin

VerificationError: Verification failed

You can also store the message + signature combined in a binary QR code:

python QRSA.py signqr --message "Joost K;2021-01-22;My Company" --key priv.key

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The generated barcode cannot be read back and verified, yet. We plan on using opencv cv2.QRCodeDetector() for this.