Using JWTs for secure digital signatures and document verification

03 Oct 2023

In the digital age, ensuring the authenticity and integrity of documents is essential. JWTs (JSON Web Tokens) provide a secure and efficient way to implement digital signatures and document verification. In this blog post, we will explore the fundamentals of JWTs and how they can be used for this purpose.

What is a JWT?

A JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact and self-contained method for securely transmitting information between parties as a JSON object. A JWT consists of three parts: header, payload, and signature.

The header typically consists of two parts: the type of the token (JWT) and the signing algorithm used (e.g., HMAC SHA256 or RSA).

Payload

The payload contains the claims, which are statements about an entity (typically the user) and additional metadata. Claims can include information such as the user’s name, role, permissions, and any custom data needed.

Signature

To create the signature, the header and payload are encoded, concatenated with a secret key, and then hashed using the specified algorithm from the header. The resulting signature can be used to verify the authenticity and integrity of the token.

Secure Digital Signatures

JWTs can be used to implement secure digital signatures. The issuer (signer) generates a JWT, signs it using their private key, and sends it along with the document. The recipient (verifier) can then use the public key of the issuer to verify the JWT’s signature and consequently the document’s authenticity.

Here’s an example of generating and verifying a JWT for document verification using the Python programming language:

import jwt

document = "Lorem ipsum dolor sit amet..."
private_key = "..."
public_key = "..."

# Generating JWT
jwt_token = jwt.encode({"document": document}, private_key, algorithm="RS256")

# Verifying JWT
try:
    decoded_token = jwt.decode(jwt_token, public_key, algorithms=["RS256"])
    
    # Do further checks on the decoded token and document...
    
    print("Signature is valid. Document verified!")
except jwt.InvalidSignatureError:
    print("Invalid signature. Document cannot be trusted.")

In the example, private_key represents the issuer’s private key, public_key represents the verifier’s public key, and document contains the document to be signed and verified. By verifying the JWT’s signature, the recipient can ensure that the document remains unchanged from the point it was signed.

Document Verification

JWTs can also be used for document verification without explicitly signing the entire document. In this scenario, the JWT contains the necessary metadata or reference to the document, and the signature verifies the authenticity and integrity of this information.

This approach is particularly useful when dealing with large documents or situations where multiple parties need to verify the same document. By securely transmitting the JWT along with the document, verification can be performed efficiently without the need for transferring the entire document.

Conclusion

Using JWTs for secure digital signatures and document verification provides a robust and efficient solution for ensuring the authenticity and integrity of documents. With the ability to sign and verify tokens using asymmetric cryptography, JWTs offer a versatile tool for implementing digital signatures and document verification in various applications.

#tech #security