发送信封数据消息

[CAPICOM 是一个仅限 32 位的组件，可用于以下操作系统：Windows Server 2008、Windows Vista 和 Windows XP。 请改用.NET Framework来实现安全功能。 有关详细信息，请参阅 使用 CAPICOM 的替代方法。]

在以下示例中，从文件读取纯文本消息，并打开包含目标邮件收件人证书的证书存储。 存储中的所有证书都作为邮件的收件人添加，邮件被信封，并且将信封邮件写入文件。

可以添加其他代码来显示要添加为消息收件人的证书、在添加为预期收件人之前验证这些证书，或者选择要添加的证书。

发生任何 CAPICOM 错误时，将返回 Err.Number 的负十进制值。 有关详细信息，请参阅 CAPICOM_ERROR_CODE。 有关 Err.Number 的正十进制值的信息，请参阅 Winerror.h。

Sub Envelope(ByVal InFile As String, ByVal OutFile As String, _
             ByVal StoreName As String)

On Error GoTo ErrorHandler

'Open the input file and read the message to be enveloped.

Dim Text As String
Open InFile For Input As #1
Input #1, Text
Close #1
If Len(Text) < 1 Then
    MsgBox "No message to be enveloped."
    Exit Sub
End If

'Open the store containing the certificates of
'the message recipients.

Dim CertStore As New Store
CertStore.Open CAPICOM_CURRENT_USER_STORE, StoreName, _
    CAPICOM_STORE_OPEN_READ_ONLY

' Check for an empty certificate store.

If CertStore.Certificates.Count < 1 Then
    MsgBox "There are no recipient certificates available."
    Set CertStore = Nothing
    Exit Sub
End If

' Declare and initialize an EnvelopedData object

Dim EnvMessage As New EnvelopedData
EnvMessage.Content = Text
Dim I As Integer
For I = 1 To CertStore.Certificates.Count
    EnvMessage.Recipients.Add CertStore.Certificates.Item(I)
    ' The following line can be uncommented to see a prompt
    ' for each certificate in the store.
    ' CertStore.Certificates.Item(I).Display
Next I

'  Set the encryption algorithm and key length. Comment out
'  or remove the following lines to use the default algorithm
'  and key length. The triple DES algorithm and 128 bit key
'  length may not be supported.
Envmessage.Algorithm.Name = ENCRYPTION_ALGORITHM_RC4
Envmessage.Algorithm.KeyLength = KEY_LENGTH_128_BITS

'Declare the string that will hold the enveloped message.

Dim EnvelopedMessage As String

'Encrypt the message into EnvelopedMessage. The enveloped message
'string contains everything that an intended recipient will need to
'decrypt the message, including information on the 
'encryption algorithm key length.
EnvelopedMessage = EnvMessage.Encrypt

' Optionally, check the length of the encrypted string to make sure 
' that the encrypt method worked.

If Len(EnvelopedMessage) < 1 Then
    MsgBox "no message encrypted. "
Else
    MsgBox " Message is " & Len(EnvelopedMessage) & " characters"

    ' Open an output file and write the encrypted message to the 
    ' file. The file is not opened if there is no message to write.
    Open OutFile For Output As #2
    Write #2, EnvelopedMessage
    Close #2
    MsgBox "The message written to file "
End If

' Release the EncryptedData object and the Store object.
Set Envmessage = Nothing
Set CertStore = Nothing

Exit Sub

ErrorHandler:
If Err.Number > 0 Then
    MsgBox "Visual Basic error found : " & Err.Description
Else
    MsgBox "CAPICOM error found : " & Err.Number
End If
End Sub