Managing the certificates

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Overview
The certificates
Using the certificates to sign a file
Using certificates to sign an email

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Managing the certificates

Overview

Signing a file allows you to check that the file was not modified or altered since it was signed. The signature also allows you to check the issuer identity.

By using the Windows certificates, WINDEV allows you to sign:

files or data strings.
emails.
executables.

The signature standard used is PKCS7.

The certificates

Two types of certificates exist:

the "qualified" certificates.
the "non-qualified" certificates.

"Qualified" certificates are delivered by a trusted authority (Verisign, Thawte, etc.) and must be purchased in most cases. "Qualified" certificates are mainly used when files are distributed outside an the organization. For example, files available for download.

"Non-qualified" certificates can be created by a user in Windows. "Non-qualified" certificates may be suitable within an organization.

Windows includes a "certificate store" in which the user certificates (also called custom certificates) are installed.

Using the certificates to sign a file

To sign a file (or a character string), WLanguage offers:

The family of CertificateXXXX functions.
The advanced Certificate type.

The principle is as follows:

Select the certificate to use via the following functions:


CertificateList	Returns the list of certificates available on the computer.
CertificateSelect	Opens a window for selecting the certificates. The listed certificates are the certificates installed in the personal store.

The certificate is stored in a variable of type Certificate that allows you to get all its characteristics.

Create the file (or string) signature using the certificate. This signature is a buffer variable that can be stored in a file, another variable, etc.
The following WLanguage functions are used to create this signature:
CertificateSignFile Creates the signature of a file. This signature can be stored in a Buffer variable or in a text file.
CertificateSignString Creates the signature of a character string.

Note: The signature is not integrated into the file, but is available separately. This method allows you to create a signature for all the file formats.

To verify a file's signature, simply check the correspondence between the file and its signature. To do so, use the following WLanguage functions:


CertificateCheckFileSignatureBuffer	Checks the correspondence between a signature and a file. The signature was stored as a Buffer variable.
CertificateCheckFileSignatureFile	Checks the correspondence between a signature and a file. The signature was kept as an external file.
CertificateCheckString	Checks the correspondence between a signature and a string.

Remarks:

You also have the ability to sign an executable via CertificateSignExecutable. In this case, the signature is included in the executable file.
You also have the ability to sign and check the signature of duplicate files. For more details, see Printing duplicates.

Using certificates to sign an email

Signing an email and its attachments allows you to check later that these elements have not been modified or altered since they were signed. The signature also allows you to check the issuer identity.

To sign an email, specify the certificate in the properties of the Email variable. The Certificate variable containing the certificate to use is associated with the Certificate property of the Email variable containing the email to be sent.

The integrity of an incoming email is checked by testing the value of the Signature property of the Email variable containing the incoming email.