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MIME S/MIME Encryption Algorithm Properties

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.

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llSuccess = .F.

loMime = createobject("CkMime")
llSuccess = loMime.SetBodyFromPlainText("This message will be encrypted.")
if (llSuccess = .F.) then
    ? loMime.LastErrorText
    release loMime
    return
endif

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

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

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

//  Load the recipient certificate (public key is sufficient for encrypting).
loCert = createobject("CkCert")
llSuccess = loCert.LoadFromFile("qa_data/recipient.cer")
if (llSuccess = .F.) then
    ? loCert.LastErrorText
    release loMime
    release loCert
    return
endif

//  Encrypt using the algorithm settings configured above.
llSuccess = loMime.Encrypt(loCert)
if (llSuccess = .F.) then
    ? loMime.LastErrorText
    release loMime
    release loCert
    return
endif

? "Encrypted with " + loMime.Pkcs7CryptAlg + " " + str(loMime.Pkcs7KeyLength) + "-bit key."


release loMime
release loCert