(PowerShell) Encrypt File to PKCS7 .p7m

PowerShell 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.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

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

$crypt = New-Object Chilkat.Crypt2

# 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
$encryptCert = New-Object Chilkat.Cert
$success = $encryptCert.LoadFromFile("/Users/chilkat/testData/cer/acme.cer")
if ($success -ne $true) {
    $($encryptCert.LastErrorText)
    exit
}

# 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.
$inFile = "/Users/chilkat/testData/pdf/sample.pdf"
$outFile = "/Users/chilkat/testData/p7m/sample.pdf.p7m"
$success = $crypt.CkEncryptFile($inFile,$outFile)
if ($success -ne $true) {
    $($crypt.LastErrorText)
    exit
}

# For demonstration purposes, a different instance of the object will be used
# for decryption.
$decrypt = New-Object Chilkat.Crypt2

# 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.
$pfxFilename = "/Users/chilkat/testData/pfx/acme.pfx"
$pfxPassword = "secret"

# Tell the component to look in the PFX file for certs and private keys.
$success = $decrypt.AddPfxSourceFile($pfxFilename,$pfxPassword)
if ($success -ne $true) {
    $($decrypt.LastErrorText)
    exit
}

# 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,$outFile)
if ($success -eq $false) {
    $($decrypt.LastErrorText)
    exit
}

$("Success!")