Post-Quantum Digital Signing for PDF Documents

Digital Portable Document Format (PDF) documents are used widely by both businesses and individuals as the electronic equivalent of paper documents. There are probably more than one trillion PDF documents in existence today, and this number will continue to grow. The contents in these documents may range from:

• Business contracts. e.g. Non-disclosure agreements, employee hiring contracts, rental agreements, sales orders, trade documentation;
• Statutory documents. e.g. electronic visas, certificates of eligibility, qualification certificates, court letters;
• Records of storage e.g. Scanned paper documents, e-printed emails.

Many of these PDF documents have long-dated validity and their proof of authenticity of these documents are required for over 10 to 25 years, depending on their contents and value they represent. Current public key digital signing techniques are inadequate to ensure the integrity and authenticity of these documents due to the threat that quantum computers bring.

In this paper, we demonstrate how we can apply post-quantum cryptography (PQC) to enhance the protection of PDF documents such that the proof of authenticity remains secure even against quantum computers, while maintaining the backwards-compatibility to existing systems and applications so that business operations are not disrupted.

This poster is published at 11th ETSI/IQC Quantum-Safe Cryptography 2025.

Available here.