(Swift 3,4,5...) Encrypt File to PKCS7 .p7m

Swift 3,4,5... 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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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    let crypt = CkoCrypt2()!

    // 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).
    crypt.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.
    crypt.pkcs7CryptAlg = "aes"
    crypt.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
    let encryptCert = CkoCert()!
    var success: Bool = encryptCert.load(fromFile: "/Users/chilkat/testData/cer/acme.cer")
    if success != true {
        print("\(encryptCert.lastErrorText!)")
        return
    }

    // Tell the crypt object to use the certificate for encrypting:
    crypt.addEncryptCert(encryptCert)

    // Encrypt a file, producing a .p7m as output.
    // The input file is unchanged, the output .p7m contains the encrypted
    // contents of the input file.
    var inFile: String? = "/Users/chilkat/testData/pdf/sample.pdf"
    var outFile: String? = "/Users/chilkat/testData/p7m/sample.pdf.p7m"
    success = crypt.ckEncryptFile(inFile, destFile: outFile)
    if success != true {
        print("\(crypt.lastErrorText!)")
        return
    }

    // For demonstration purposes, a different instance of the object will be used
    // for decryption.
    let decrypt = CkoCrypt2()!

    // 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.
    var pfxFilename: String? = "/Users/chilkat/testData/pfx/acme.pfx"
    var pfxPassword: String? = "secret"

    // Tell the component to look in the PFX file for certs and private keys.
    success = decrypt.addPfxSourceFile(pfxFilename, password: pfxPassword)
    if success != true {
        print("\(decrypt.lastErrorText!)")
        return
    }

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

    // Decrypt the .p7m
    inFile = "/Users/chilkat/testData/p7m/sample.pdf.p7m"
    outFile = "/Users/chilkat/testData/pdf/recovered.pdf"
    success = decrypt.ckDecryptFile(inFile, destFile: outFile)
    if success == false {
        print("\(decrypt.lastErrorText!)")
        return
    }

    print("Success!")

}