Cryptographic algorithms

// get a certificate with a private key
var certificate = Certificate.LoadPfx("mycert.pfx", "password");

// load the content of a file we need to sign
byte[] content = File.ReadAllBytes("document.pdf");
var contentInfo = new ContentInfo(content);

// create a PKCS #7 SignedData object based on this,
// the second argument specifies "detached" style
var signedData = new SignedData(contentInfo, true);

// add one ore more signers
var signer = new SignerInfo(certificate);
signedData.SignerInfos.Add(signer);

// create the signature
signedData.Sign();

// save the signature into a detached signature file
using (var output = File.Create("document.pdf.p7s"))
{
    signedData.Save(output);
}

' get a certificate with a private key
Dim cert = Certificate.LoadPfx("mycert.pfx", "password")

' load the content of a file we need to sign
Dim content As Byte() = File.ReadAllBytes("document.pdf")
Dim contentInfo = New ContentInfo(content)

' create a PKCS #7 SignedData object based on this,
' the second argument specifies "detached" style
Dim signedData = New SignedData(contentInfo, True)

' add one ore more signers
Dim signer = New SignerInfo(cert)
signedData.SignerInfos.Add(signer)

' create the signature
signedData.Sign()

' save the signature into a detached signature file
Using output = File.Create("document.pdf.p7s")
    signedData.Save(output)
End Using

// load the content of a file whose signature we wish to check
byte[] content = File.ReadAllBytes("document.pdf");
var contentInfo = new ContentInfo(content);

// create a PKCS #7 SignedData object base on this,
// the second argument specifies "detached" style
var signedData = new SignedData(contentInfo, true);

// load the detached signature file
using (Stream input = File.OpenRead("document.pdf.p7s"))
{
    signedData.Load(input);
}

// validate the signature and the certificates
SignatureValidationResult result = signedData.Validate();

// display the validation result
if (result.Valid)
{
    Console.WriteLine("Both signature and certificates are valid.");
}
else
{
    Console.WriteLine("Signature or certificates are NOT valid.");
    Console.WriteLine("Signature problems: {0}", result.Status);
    Console.WriteLine("Certificate problems: {0}", result.CertificateValidationStatus);
}

' load the content of a file whose signature we wish to check
Dim content As Byte() = File.ReadAllBytes("document.pdf")
Dim contentInfo = New ContentInfo(content)

' create a PKCS #7 SignedData object base on this,
' the second argument specifies "detached" style
Dim signedData = New SignedData(contentInfo, True)

' load the detached signature file
Using input As Stream = File.OpenRead("document.pdf.p7s")
    signedData.Load(input)
End Using

' validate the signature and the certificates
Dim result As SignatureValidationResult = signedData.Validate()

' display the validation result
If result.Valid Then
    Console.WriteLine("Both signature and certificates are valid.")
Else
    Console.WriteLine("Signature or certificates are NOT valid.")
    Console.WriteLine("Signature problems: {0}", result.Status)
    Console.WriteLine("Certificate problems: {0}", result.CertificateValidationStatus)
End If

// get the recipient's certificate
// (no private key needed)
var certificate = Certificate.LoadDer("theircert.cer");

// load the content of a file we need to encrypt
byte[] content = File.ReadAllBytes("document.pdf");
var contentInfo = new ContentInfo(content);

// create a PKCS #7 EnvelopedData object based on this
var envelopedData = new EnvelopedData(contentInfo);

// add one ore more recipients
var recipient = new KeyTransRecipientInfo(certificate);
envelopedData.RecipientInfos.Add(recipient);

// encrypt data
envelopedData.Encrypt();

// save encrypted data into a .p7m file
using (var output = File.Create("document.p7m"))
{
    envelopedData.Save(output);
}

' get the recipient's certificate
' (no private key needed)
Dim cert = Certificate.LoadDer("theircert.cer")

' load the content of a file we need to encrypt
Dim content As Byte() = File.ReadAllBytes("document.pdf")
Dim contentInfo = New ContentInfo(content)

' create a PKCS #7 EnvelopedData object based on this
Dim envelopedData = New EnvelopedData(contentInfo)

' add one ore more recipients
Dim recipient = New KeyTransRecipientInfo(cert)
envelopedData.RecipientInfos.Add(recipient)

' encrypt data
envelopedData.Encrypt()

' save encrypted data into a .p7m file
Using output = File.Create("document.p7m")
    envelopedData.Save(output)
End Using

// create an empty PKCS #7 EnvelopedData object
var envelopedData = new EnvelopedData();

// load the encrypted file into it
using (Stream input = File.OpenRead("document.p7m"))
{
    envelopedData.Load(input);
}

// check whether it's possible to decrypt the file
if (envelopedData.HasPrivateKey)
{
    // decrypt it if possible (when a suitable decryption certificate with
    // an associated private key is available in Windows Certificate store)
    envelopedData.Decrypt();

    // save decrypted content into a file
    File.WriteAllBytes("document.pdf", envelopedData.ContentInfo.ToArray());
}
else
{
    // otherwise, display a list of intended recipients
    foreach (RecipientInfo recipient in envelopedData.RecipientInfos)
    {
        SubjectIdentifier id = recipient.RecipientIdentifier;
        Console.WriteLine("Recipient info:");

        if (id.Issuer != null)
            Console.WriteLine("  Certificate issuer: {0}", id.Issuer);

        if (id.SerialNumber != null)
            Console.WriteLine("  Serial number: {0}", BitConverter.ToString(id.SerialNumber));

        if (id.SubjectKeyIdentifier != null)
            Console.WriteLine("  Subject key identifier: {0}", BitConverter.ToString(id.SubjectKeyIdentifier));

        if (id.PublicKey != null)
            Console.WriteLine("  Public key: {0}", BitConverter.ToString(id.PublicKey));

        if (id.PublicKeyAlgorithm != null)
            Console.WriteLine("  Key algorithm: {0}", id.PublicKeyAlgorithm.Oid);
    }
}

' create an empty PKCS #7 EnvelopedData object
Dim envelopedData = New EnvelopedData()

' load the encrypted file into it
Using input As Stream = File.OpenRead("document.p7m")
    envelopedData.Load(input)
End Using

' check whether it's possible to decrypt the file
If envelopedData.HasPrivateKey Then
    ' decrypt it if possible (when a suitable decryption certificate with
    ' an associated private key is available in Windows Certificate store)
    envelopedData.Decrypt()

    ' save decrypted content into a file
    File.WriteAllBytes("document.pdf", envelopedData.ContentInfo.ToArray())
Else
    ' otherwise, display a list of intended recipients
    For Each recipient As RecipientInfo In envelopedData.RecipientInfos
        Dim id As SubjectIdentifier = recipient.RecipientIdentifier
        Console.WriteLine("Recipient info:")

        If id.Issuer IsNot Nothing Then
            Console.WriteLine("  Certificate issuer: {0}", id.Issuer)
        End If

        If id.SerialNumber IsNot Nothing Then
            Console.WriteLine("  Serial number: {0}", BitConverter.ToString(id.SerialNumber))
        End If

        If id.SubjectKeyIdentifier IsNot Nothing Then
            Console.WriteLine("  Subject key identifier: {0}", BitConverter.ToString(id.SubjectKeyIdentifier))
        End If

        If id.PublicKey IsNot Nothing Then
            Console.WriteLine("  Public key: {0}", BitConverter.ToString(id.PublicKey))
        End If

        If id.PublicKeyAlgorithm IsNot Nothing Then
            Console.WriteLine("  Key algorithm: {0}", id.PublicKeyAlgorithm.Oid)
        End If
    Next
End If