Sign Method

Signs the current message.

Syntax

int Sign();

Remarks

Sign digitally signs the input data with the the specified certificate(s). Certificates are specified by calling AddCertificate or setting the Certificates property.

OutputFormat specifies the encoding of the output message. Valid values are PEM, DER, and SMIME. IncludeCertificates specifies whether the public certificate is included in the signed message. Additional settings allow further configuration. The following properties are applicable when calling this method:

• Certificates (required)
• DetachedSignature
• EnableCompression
• GenerateSignatureTimestamp
• IncludeCertificates
• OutputFormat
• SignatureHashAlgorithm
• UsePSS

Input and Output Properties

The class will determine the source and destination of the input and output based on which properties are set.

The order in which the input properties are checked is as follows:

• InputFile
• InputMessage

When a valid source is found the search stops. The order in which the output properties are checked is as follows:

• OutputFile
• OutputMessage: The output data is written to this property if no other destination is specified.

Sign and Verify a message

Cms cms = new Cms();
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
cms.InputMessage = "My Data";
cms.Sign();

string signedMessage = cms.OutputMessage;

cms = new Cms();
cms.InputMessage = signedMessage;
cms.VerifySignature();

string plaintextMessage = cms.OutputMessage;

Cms cms = new Cms();
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
cms.InputMessage = "My Data";
cms.OutputFormat = "DER";
cms.Sign();

byte[] signedMessage = cms.OutputMessageB; //Binary output

cms = new Cms();
cms.InputMessageB = signedMessage;
cms.VerifySignature();

string plaintextMessage = cms.OutputMessage;

Cms cms = new Cms();
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
cms.InputMessage = "My Data";
cms.DetachedSignature = true;
cms.Sign();

string signature = cms.OutputMessage;

cms = new Cms();
cms.InputMessage = "My Data";
cms.DetachedSignatureData = signature;
cms.DetachedSignature = true;
cms.VerifySignature();

Cms cms = new Cms();
cms.InputMessage = "My Data";
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test2.pfx", "password2", "*"));
cms.Sign();

string signedMessage = cms.OutputMessage;

cms = new Cms();
cms.InputMessage = signedMessage;
cms.VerifySignature();

string plaintextMessage = cms.OutputMessage;

Cms cms = new Cms();
cms.InputMessage = "My Data";
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
cms.IncludeCertificates = CmsIncludeCertificates.icsNone;
cms.Sign();

string signedMessage = cms.OutputMessage;

cms = new Cms();
cms.OnSignerCertInfo += (s, e) => {
  Console.WriteLine(e.Issuer);
  Console.WriteLine(e.SerialNumber);
  if (e.Issuer == "CN=100") //Identify the certificate to load based on event params
  {
    //Load the correct signer certificate.
    cms.SignerCerts.Add(new Certificate(CertStoreTypes.cstPublicKeyFile, @"C:\temp\test.cer", "", "*"));
  }
};
cms.InputMessage = signedMessage;
cms.VerifySignature();

string plaintextMessage = cms.OutputMessage;

Error Handling

This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)