(Lianja) Encrypt File to PKCS7 .p7m

Lianja example to public-key encrypt a file creating a PKCS#7 .p7m file as output. Also demonstrates how to decrypt the .p7m to recover the original file.

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

loCrypt = createobject("CkCrypt2")

// Indicate the public-key encryption is to be used.
// Do this by setting the encryption algorithm equal 
// to "PKI" (an acroynm for public-key infrastructure).
loCrypt.CryptAlgorithm = "PKI"

// Indicate the inner symmetric encryption algorithm to be used.
// possible values are "aes", "des", "3des", and "rc2".
// For this example, we'll use 256-bit AES encryption.
loCrypt.Pkcs7CryptAlg = "aes"
loCrypt.KeyLength = 256

// To encrypt, only a certificate w/ public key is needed.
// (The certificate w/ private key is required for decryption.)

// The LoadFromFile method can load virtually any certificate format:
// 1. DER encoded binary X.509 (.CER)
// 2. Base-64 encoded X.509 (.CER)
// 3. Cryptographic Message Syntax Standard - PKCS #7 Certificates (.P7B)
// 4. PEM format
loEncryptCert = createobject("CkCert")
llSuccess = loEncryptCert.LoadFromFile("/Users/chilkat/testData/cer/acme.cer")
if (llSuccess <> .T.) then
    ? loEncryptCert.LastErrorText
    release loCrypt
    release loEncryptCert
    return
endif

// Tell the crypt object to use the certificate for encrypting:
loCrypt.AddEncryptCert(loEncryptCert)

// Encrypt a file, producing a .p7m as output.
// The input file is unchanged, the output .p7m contains the encrypted
// contents of the input file.
lcInFile = "/Users/chilkat/testData/pdf/sample.pdf"
lcOutFile = "/Users/chilkat/testData/p7m/sample.pdf.p7m"
llSuccess = loCrypt.CkEncryptFile(lcInFile,lcOutFile)
if (llSuccess <> .T.) then
    ? loCrypt.LastErrorText
    release loCrypt
    release loEncryptCert
    return
endif

// For demonstration purposes, a different instance of the object will be used
// for decryption.
loDecrypt = createobject("CkCrypt2")

// To decrypt, the certificate w/ private key is required.  A PFX (also known
// as PKCS#12) is a common secure container for certs and private keys.
lcPfxFilename = "/Users/chilkat/testData/pfx/acme.pfx"
lcPfxPassword = "secret"

// Tell the component to look in the PFX file for certs and private keys.
llSuccess = loDecrypt.AddPfxSourceFile(lcPfxFilename,lcPfxPassword)
if (llSuccess <> .T.) then
    ? loDecrypt.LastErrorText
    release loCrypt
    release loEncryptCert
    release loDecrypt
    return
endif

// Tell the decrypt object that PKI (public key encryption) is to be used
// for decryptiong.
loDecrypt.CryptAlgorithm = "PKI"
// There is no need to set the Pkcs7Alg or KeyLength because this information
// is contained within the .p7m

// Decrypt the .p7m
lcInFile = "/Users/chilkat/testData/p7m/sample.pdf.p7m"
lcOutFile = "/Users/chilkat/testData/pdf/recovered.pdf"
llSuccess = loDecrypt.CkDecryptFile(lcInFile,lcOutFile)
if (llSuccess = .F.) then
    ? loDecrypt.LastErrorText
    release loCrypt
    release loEncryptCert
    release loDecrypt
    return
endif

? "Success!"


release loCrypt
release loEncryptCert
release loDecrypt