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pkcs7-parser-rs

Rust parser for PKCS#7 / CMS signed data structures.
This library is used to extract and deserialize cryptographic information from .p7b or .p7s files, and is currently employed in the zkID_Wallet project.

📦 About

This crate provides a low-level parser for files encoded using PKCS#7 (Public-Key Cryptography Standards #7), now formally known as Cryptographic Message Syntax (CMS) as defined in RFC 5652.

Although CMS is the current standard, the term PKCS#7 is still widely used in practical contexts and tooling (e.g., .p7b or .pkcs7 file extensions), and therefore we keep this naming convention for familiarity and clarity.

The goal of this parser is to extract raw signed data, certificates, CRLs, and signer metadata in a structured and reusable way — suitable for further cryptographic processing, such as signature verification or identity attestation in zero-knowledge systems.

🔍 Extracted Structures

Given a .p7b file, the parser decodes several nested structures including:

  • Pkcs7: Root container (with content type and signed data)
  • SignedData: Core structure with digest algorithms, content, certificates and CRLs
  • Certificate, TbsCertificate: X.509 certificate
  • CertificateList, TbsCertList: CRL (Certificate Revocation List)
  • SignerInfo, SignerIdentifier: Signer metadata
  • Attribute, Extension, AlgorithmIdentifier, Name structures
  • Optimized structs (CertificateData, CrlData) are also provided for serialization (e.g., for sending to guest code in zkVM environments).

Example extracted struct (simplified):

#[derive(Debug)]
pub struct Pkcs7 {
    pub content_type: Oid,
    pub content: SignedData,
    pub content_bytes: Vec<u8>,
}

🔗 Used in zkID_Wallet

This library was originally developed as part of zkCF_Wallet, a university thesis project focused on digital identity and zero-knowledge proof integration.

It is now a standalone component of the more advanced zkID_Wallet, a modular and privacy-preserving identity wallet that leverages zero-knowledge cryptography to prove identity attributes without revealing them.