The Sign method creates a digital signature on the content to be signed. A digital signature consists of a hash of the content to be signed that is encrypted by using the private key of the signer. This method can only be used after the SignedData.Content property has been initialized. If the Sign method is called on an object that already has a signature, the old signature is replaced. The signature is created by using the SHA1 signing algorithm.
- Signer [in, optional]
A reference to the Signer object of the signer of the data. The Signer object must have access to the private key of the certificate used to sign. This parameter can be NULL; for more information, see Remarks.
- bDetached [in, optional]
If True, the data to be signed is detached; that is, the content that is signed is not included as part of the signed object. To verify the signature on detached content, an application must have a copy of the original content. Detached content is often used to decrease the size of a signed object to be sent across the web, if the recipient of the signed message has an original copy of the signed data. The default value is False.
- EncodingType [in, optional]
A value of the CAPICOM_ENCODING_TYPE enumeration that indicates how the signed data is to be encoded. The default value is CAPICOM_ENCODE_BASE64. This parameter can be one of the following values.
This method returns a string that contains the encoded, signed data.
If this method fails, an error will be thrown. The Err object will contain additional information about the error.
Because creating a digital signature requires the use of a private key, web-based applications that attempt to use this method will require user interface prompts that allow the user to approve the use of the private key, for security reasons.
The following results apply to the Signer parameter value:
- If the Signer parameter is not NULL, this method uses the private key pointed to by the associated certificate to encrypt the signature. If the private key pointed to by the certificate is not available, the method fails.
- If the Signer parameter is NULL and there is exactly one certificate in the CURRENT_USER MY store that has access to a private key, that certificate is used to create the signature.
- If the Signer parameter is NULL, the Settings.EnablePromptForCertificateUI property value is true, and there is more than one certificate in the CURRENT_USER MY store with an available private key, a dialog box appears that allows the user to select which certificate is used.
- If the Signer parameter is NULL and the Settings.EnablePromptForCertificateUI property is false, the method fails.
- If the Signer parameter is NULL and there is no certificate in the CURRENT_USER MY store with an available private key, the method fails.
CAPICOM 2.0 or later on Windows Server 2003 and Windows XP