Xbase++

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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LOCAL nSuccess
LOCAL oMime
LOCAL oCert

nSuccess := 0

oMime := CreateObject("Chilkat.Mime")
nSuccess := oMime:SetBodyFromPlainText("This message will be encrypted.")
IF (nSuccess == 0)
    ? oMime:LastErrorText
    oMime:destroy()
    RETURN
ENDIF

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

//  Pkcs7KeyLength is the content-encryption key length in bits.  The default is 128.
oMime: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.
oMime:OaepPadding := 1
oMime:OaepHash := "sha256"
oMime:OaepMgfHash := "sha256"

//  Load the recipient certificate (public key is sufficient for encrypting).
oCert := CreateObject("Chilkat.Cert")
nSuccess := oCert:LoadFromFile("qa_data/recipient.cer")
IF (nSuccess == 0)
    ? oCert:LastErrorText
    oMime:destroy()
    oCert:destroy()
    RETURN
ENDIF

//  Encrypt using the algorithm settings configured above.
nSuccess := oMime:Encrypt(oCert)
IF (nSuccess == 0)
    ? oMime:LastErrorText
    oMime:destroy()
    oCert:destroy()
    RETURN
ENDIF

? "Encrypted with " + oMime:Pkcs7CryptAlg + " " + Str(oMime:Pkcs7KeyLength) + "-bit key."

oMime:destroy()
oCert:destroy()