(C#) Extract PKCS7 Signature Digest

Demonstrates how to extract a signature digest from a PKCS7 signature.

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// This example requires the Chilkat Crypt API to have been previously unlocked.
// See Unlock Chilkat Crypt for sample code.

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

string p7mFile = "qa_data/p7m/test.pdf.p7m";
string outPath = "qa_output/test.pdf";

// First let's see if this .p7m signature can be verified, and the original file extracted.
bool verified = crypt.VerifyP7M(p7mFile,outPath);
if (verified != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

// How many signers?
// (The NumSignerCerts property is set whenever a signature is verified.)
Debug.WriteLine("Num Signers: " + Convert.ToString(crypt.NumSignerCerts));

// Load the .p7m into memory...
Chilkat.BinData pkcs7Data = new Chilkat.BinData();
pkcs7Data.LoadFile(p7mFile);

// Check to see if this .p7m contains the binary bytes, or if it's
// already base64 encoded.  Get the 1st two bytes.  If the first two 
// bytes are the us-ascii values "MI", then we have base64.
Chilkat.StringBuilder sbBase64 = new Chilkat.StringBuilder();
string hexStr = pkcs7Data.GetEncodedChunk(0,2,"hex");
sbBase64.Append(hexStr);

bool bHaveBase64 = false;
if (sbBase64.ContentsEqual("4D49",true) == true) {
    bHaveBase64 = true;
    sbBase64.Clear();
    sbBase64.AppendBd(pkcs7Data,"utf-8",0,0);
}

// Get each signer's signature digest.
crypt.EncodingMode = "base64";
int i = 0;
string digest;
while (i < crypt.NumSignerCerts) {
    if (bHaveBase64) {
        digest = crypt.Pkcs7ExtractDigest(i,sbBase64.GetAsString());
    }
    else {
        digest = crypt.Pkcs7ExtractDigest(i,pkcs7Data.GetEncoded("base64"));
    }

    if (crypt.LastMethodSuccess != true) {
        Debug.WriteLine(crypt.LastErrorText);
        return;
    }

    Debug.WriteLine("Signer " + Convert.ToString(i + 1) + " digest = " + digest);
    i = i + 1;
}