Digitally Signing XML files

[criadoperez]

As we continue to integrate blockchain technology with decentralized storage solutions like IPFS, ensuring the authenticity and integrity of data becomes crucial. One critical aspect is digitally signing XML files, which are commonly used in DDEX messages. This post explores two primary methods for digitally signing XML files and their implications, particularly when signatures might need to be verified on-chain.

Option 1: Using Ethereum Private Key for Signatures

Pros:

Native Support: Ethereum’s EVM natively supports secp256k1 signatures, making it straightforward to verify signatures on-chain using the ecrecover function.
Efficiency: Verifying signatures in smart contracts is efficient and cost-effective.
Integration: Easy integration with existing Ethereum wallets and key management systems.

Cons:

Non-Standard: This method does not adhere to the XMLDSig standard, requiring custom implementation for including and managing signatures within XML documents.

Example Workflow:

Sign the Data: Hash the XML data and sign it using an Ethereum private key.
Store on IPFS: Upload the signed XML file to IPFS.
Verify On-Chain: Use a smart contract to verify the signature by recovering the signer’s address from the hash and comparing it to an expected address.

Option 2: Using XMLDSig (XML Digital Signatures)

Pros:

Standardized: Adheres to the XMLDSig standard, ensuring compatibility with various systems and tools that manage XML documents.
Interoperability: Easier integration with systems that already use XMLDSig for signing and verifying XML documents.

Cons:

Complex Verification: Verifying XMLDSig signatures on-chain is not natively supported and would require implementing complex cryptographic operations in Solidity, which is gas-intensive and impractical.
Cost: The complexity of on-chain verification makes it significantly more expensive in terms of gas fees.

Example Workflow:

Sign the Data: Use XMLDSig to sign the XML document with a private key.
Store on IPFS: Upload the signed XML file to IPFS.
Verify Off-Chain: Use external systems to verify the XMLDSig signature. Implementing on-chain verification is complex and costly.

Conclusion

Both methods have their merits and challenges. Using Ethereum private key signatures offers efficiency and native support for on-chain verification but lacks standardization. In contrast, XMLDSig provides a standardized approach but presents significant challenges for on-chain verification due to its complexity and cost.