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Xojo Plugin

MIME S/MIME Encryption Algorithm Properties

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Demonstrates the properties that control S/MIME encryption: Pkcs7CryptAlg (the symmetric content-encryption algorithm), Pkcs7KeyLength (the content-encryption key length in bits), OaepPadding (whether RSAES-OAEP key transport is used instead of RSAES-PKCS1-v1_5), and the OAEP hash settings OaepHash and OaepMgfHash. The properties are configured before calling Encrypt.

Background. CMS/PKCS #7 encryption uses a symmetric algorithm to protect the content and an RSA key-transport scheme to protect the symmetric key. The defaults (aes, 128-bit, PKCS1-v1_5 padding) work broadly; these properties tune the algorithms and padding.

Chilkat Xojo Plugin Downloads

Xojo Plugin
Dim success As Boolean
success = False

Dim mime As New Chilkat.Mime
success = mime.SetBodyFromPlainText("This message will be encrypted.")
If (success = False) Then
    System.DebugLog(mime.LastErrorText)
    Return
End If

//  Pkcs7CryptAlg is the symmetric content-encryption algorithm.  Supported values are aes, aes-gcm,
//  des, 3des, and rc2.  The default is aes.
mime.Pkcs7CryptAlg = "aes"

//  Pkcs7KeyLength is the content-encryption key length in bits.  The default is 128.
mime.Pkcs7KeyLength = 256

//  OaepPadding selects the RSA key-transport padding.  The default is 0 (RSAES-PKCS1-v1_5).
//  Set 1 to use RSAES-OAEP, in which case the OAEP hash settings apply.
mime.OaepPadding = True
mime.OaepHash = "sha256"
mime.OaepMgfHash = "sha256"

//  Load the recipient certificate (public key is sufficient for encrypting).
Dim cert As New Chilkat.Cert
success = cert.LoadFromFile("qa_data/recipient.cer")
If (success = False) Then
    System.DebugLog(cert.LastErrorText)
    Return
End If

//  Encrypt using the algorithm settings configured above.
success = mime.Encrypt(cert)
If (success = False) Then
    System.DebugLog(mime.LastErrorText)
    Return
End If

System.DebugLog("Encrypted with " + mime.Pkcs7CryptAlg + " " + Str(mime.Pkcs7KeyLength) + "-bit key.")