(PowerShell) Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

Chilkat .NET Downloads Chilkat .NET Assemblies

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

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

$crypt = New-Object Chilkat.Crypt2

# Tell the crypt object to use 3 certificates.
# Do this by calling AddEncryptCert for each certificate.

# Load a digital certificate. 
# We don't need the private key for encryption.
# Only the public key is needed (which is included in a certificate).
$cert1 = New-Object Chilkat.Cert
$success = $cert1.LoadFromFile("qa_data/user1/cert_user1.pem")
# Assume success for the example, but make sure your application checks for success/failure...
$crypt.AddEncryptCert($cert1)

$cert2 = New-Object Chilkat.Cert
$success = $cert2.LoadFromFile("qa_data/user2/cert_user2.pem")
$crypt.AddEncryptCert($cert2)

$cert3 = New-Object Chilkat.Cert
$success = $cert3.LoadFromFile("qa_data/user3/cert_user3.pem")
$crypt.AddEncryptCert($cert3)

# Indicate that we want PKI encryption (i.e. public-key infrastructure)
# to produce a CMS message (Cryptographic Message Syntax/PKCS7),
# that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
# bulk encryption.
$crypt.CryptAlgorithm = "pki"
$crypt.Pkcs7CryptAlg = "aes"
$crypt.KeyLength = 128
$crypt.OaepHash = "sha256"
$crypt.OaepPadding = $true

# Load the file to be encrypted...
$fileData = New-Object Chilkat.BinData
$success = $fileData.LoadFile("qa_data/jpg/penguins.jpg")
# Your app should check for success/failure..

# Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
$success = $crypt.EncryptBd($fileData)
if ($success -ne $true) {
    $($crypt.LastErrorText)
    exit
}

# Save the PKCS7 encrypted message to a file..
$success = $fileData.WriteFile("qa_output/pkcs7_encrypted.p7")

# Now indicate that the PKCS7 output is to be returned in the base64 encoding.
$crypt.EncodingMode = "base64"

$("OK.")