Decrypt Method

Decrypts the current message.

Syntax

cms.decrypt([callback])

Callback

The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).

The callback for this method is defined as:

function(err){ }

'err' is the error that occurred. If there was no error, then 'err' is 'null'.

'err' has 2 properties which hold detailed information:

err.code
err.message

Remarks

Decrypt decrypts the input data with the specified certificate. Certificates are specified by calling AddCertificate or setting the Certificates property.

If the certificate used to encrypt the message is not known ahead of time GetRecipientInfo may be called prior to calling Decrypt to obtain information about the recipient (the entity the for which the message was encrypted). If GetRecipientInfo is called, the RecipientInfo event is fired with information about the recipient which may be used to load an appropriate decryption certificate.

The following properties are applicable when calling this method:

• Certificates (Required)

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.

Encrypt and Decrypt a message

Cms cms = new Cms();
cms.RecipientCerts.Add(new Certificate(CertStoreTypes.cstPublicKeyFile, @"C:\temp\test.cer", "", "*"));
cms.InputMessage = "My Data";
cms.Encrypt();

string encryptedMessage = cms.OutputMessage;

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

string plaintextMessage = cms.OutputMessage;

Cms cms = new Cms();
cms.RecipientCerts.Add(new Certificate(CertStoreTypes.cstPublicKeyFile, @"C:\temp\test.cer", "", "*"));
cms.InputMessage = "My Data";
cms.OutputFormat = "DER";
cms.Encrypt();

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

cms = new Cms();
cms.InputMessageB = encryptedMessage;
cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
cms.Decrypt();

string plaintextMessage = cms.OutputMessage;

Cms cms = new Cms();
cms.RecipientCerts.Add(new Certificate(CertStoreTypes.cstPublicKeyFile, @"C:\temp\test.cer", "", "*"));
cms.RecipientCerts.Add(new Certificate(CertStoreTypes.cstPublicKeyFile, @"C:\temp\test2.cer", "", "*"));
cms.InputMessage = "My Data";
cms.Encrypt();

string encryptedMessage = cms.OutputMessage;

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

string plaintextMessage = cms.OutputMessage;

Cms cms = new Cms();
cms.RecipientCerts.Add(new Certificate(CertStoreTypes.cstPublicKeyFile, @"C:\temp\test.cer", "", "*"));
cms.InputMessage = "My Data";
cms.Encrypt();

string encryptedMessage = cms.OutputMessage;

//If the recipient certificate is not known ahead of time the GetRecipientInfo method may be called
//to find information about the certificate.
cms = new Cms();
cms.InputMessage = encryptedMessage;
cms.OnRecipientInfo += (s, e) => {
  Console.WriteLine(e.SerialNumber);
  Console.WriteLine(e.Issuer);
  if (e.Issuer == "CN=100") //Identify the certificate to load based on event params
  {
    cms.Certificates.Add(new Certificate(CertStoreTypes.cstPFXFile, @"C:\temp\test.pfx", "password", "*"));
  }
};

cms.GetRecipientInfo();
cms.Decrypt();

string plaintextMessage = cms.OutputMessage;