Attacks on PDF Certification (May 2021)🔒 SSL Verified

Table of Contents

• ↓ Authority Metrics: Score 76/100
• ↓ Global Reach of Pdf-insecurity
• ↓ Competitor Analysis for .ORG Domains
• ↓ Top Alternatives to pdf-insecurity.org

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"Approval signatures testify a specific document state. The specification allows the usage of multiple signatures on the same document. Any other change on a signed document leads to an invalidation of the approval signature or warnings in most PDF viewers. Hereafter, we use the terms signature and signed document for approval signatures."

"Certification signatures provide a more powerful and flexible mechanism to handle digitally signed documents. During the document’s certification, the owner defines a list of allowed modifications that do not invalidate the document’s certification signature. These allowed modifications can be a subset of the following actions: writing text to specific form fields (even without signing the document), providing annotations to the document, or adding approval signatures. Since a certification signature sets permissions on the entire document, only one certification signature is allowed within a PDF document. This certification signature must also be the first signature in the PDF. Hereafter, we use the terms certification and certified document for certification signatures."

"We investigate the following question: How dangerous are permitted changes in certified documents?. To answer this question we systematically analyze the allowed modifications in certified documents and reveal two new vulnerabilities abusing flaws in the PDF specification: Evil Annotation Attack (EAA) and Sneaky Signature Attack (SSA). These vulnerabilities allow an attacker to change the visible content of a PDF document by displaying malicious content over the certified content. Nevertheless, the certification remains valid and the application shows no warnings."

"We evaluated 26 PDF applications and were able to break the security of certified documents in 24 of them. Additionally, we analyzed 26 applications to determine whether the permissions for adding annotations and signatures, as defined in the PDF specification, were implemented correctly. We show that for 11 of 26 applications, a permission mismatch exists."

Key Topics & Focus Areas for pdf-insecurity.org:

Authority Metrics: Score 76/100

Global Reach of Pdf-insecurity

Competitor Analysis for .ORG Domains