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Create and Verify Digital Signature
Uses Chilkat Crypt2 to create and verify a detached digital signature. Dim crypt As New ChilkatCrypt2 crypt.UnlockComponent "test" ' Select a digital certificate for signing. Dim StoreCreator As ChilkatCreateCS Set StoreCreator = New ChilkatCreateCS ' Create a certificate store object representing the registry-based ' current user certificate store. Dim certStore As ChilkatCertStore Set certStore = StoreCreator.OpenCurrentUserStore() ' Find a certificate matching an email address. Dim cert As ChilkatCert Set cert = certStore.FindCertBySubjectE("test@chilkatsoft.com") If (cert Is Nothing) Then MsgBox "Certificate not found!" Exit Sub End If ' Use this certificate. crypt.SetSigningCert cert Dim fileData As Variant Dim sigData As Variant fileData = crypt.ReadFile("sample.pdf") If IsNull(fileData) Then MsgBox crypt.LastErrorText Exit Sub End If sigData = crypt.SignBytes(fileData) If IsNull(sigData) Then MsgBox crypt.LastErrorText Exit Sub End If success = crypt.WriteFile("signature.dat", sigData) If (success = 0) Then MsgBox crypt.LastErrorText End If MsgBox "OK!" ' Now verify it... Dim sigData2 As Variant sigData2 = crypt.ReadFile("signature.dat") If IsNull(sigData2) Then MsgBox crypt.LastErrorText Exit Sub End If sigOK = crypt.VerifyBytes(fileData, sigData2) If (sigOK = 1) Then MsgBox "Signature is valid, the file is unchanged." Else MsgBox "Invalid signature, the file may have been altered." End If
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