MIME S/MIME Signing Algorithm Properties

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Demonstrates the properties that control S/MIME signing: SigningAlg (the RSA signature scheme, PKCS1-V1_5 or RSASSA-PSS), SigningHashAlg (the message-digest algorithm), Micalg and Protocol (the micalg and protocol parameters of a multipart/signed Content-Type), and UseXPkcs7 (whether historical x-pkcs7 media-type names are used). The properties are configured before creating a detached signature.

Dim success As Boolean = False

Dim mime As ChilkatMime
mime.Initialize
success = mime.SetBodyFromPlainText("This message will be signed.")
If success = False Then
    Log(mime.LastErrorText)
    Return
End If


'  SigningAlg is the RSA signature scheme.  The default is PKCS1-V1_5; set RSASSA-PSS (or pss) for
'  RSASSA-PSS.
mime.SigningAlg = "PKCS1-V1_5"

'  SigningHashAlg is the message-digest algorithm.  The default is sha256.
mime.SigningHashAlg = "sha256"

'  Micalg and Protocol are the micalg and protocol parameters written into a multipart/signed
'  Content-Type header field.  They are normally set automatically, but can be controlled here.
mime.Micalg = "sha-256"
mime.Protocol = "application/pkcs7-signature"

'  UseXPkcs7 controls whether newly created S/MIME media types use the historical x-pkcs7 names.
mime.UseXPkcs7 = False

'  Load a signing certificate (with private key access) from a PFX.  The PFX password should come
'  from a secure source rather than being hard-coded.
Dim pfxPassword As String = "myPfxPassword"
Dim cert As ChilkatCert
cert.Initialize("cert")
success = cert.LoadPfxFile("qa_data/signer.pfx", pfxPassword)
If success = False Then
    Log(cert.LastErrorText)
    Return
End If


'  Create the detached signature using the algorithms configured above.
success = mime.AddDetachedSignature(cert)
If success = False Then
    Log(mime.LastErrorText)
    Return
End If


Log("Signed with SigningAlg=" & mime.SigningAlg & " SigningHashAlg=" & mime.SigningHashAlg)