(PowerShell) Encrypt/Decrypt using PFX to produce -----BEGIN PKCS7----- ... -----END PKCS7-----

First we encrypt using a certificate + public key to produce output such as:

-----BEGIN PKCS7-----
MIIHPwYJKoZIhvcNAQcEoIIHMDCCBywC ...
...
...
-----END PKCS7-----

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

# Specify the encryption to be used.
# "pki" indicates "Public Key Infrastructure" and will create a PKCS7 encrypted (enveloped) message.
$crypt.CryptAlgorithm = "pki"
$crypt.Pkcs7CryptAlg = "aes"
$crypt.KeyLength = 128
$crypt.OaepHash = "sha256"
$crypt.OaepPadding = $true

# A certificate is needed as the encryption key.
# Althought the PFX contains the associated private key, we don't need it for encryption.
# (A certificate usually contains the public key by default.)
$cert = New-Object Chilkat.Cert
$success = $cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
if ($success -ne $true) {
    $($cert.LastErrorText)
    exit
}

# Tell the crypt object to use the certificate.
$crypt.SetEncryptCert($cert)

$toBeEncrypted = "This string is to be encrypted."

# Get the result in multi-line BASE64 MIME format.
$crypt.EncodingMode = "base64_mime"

$encryptedStr = $crypt.EncryptStringENC($toBeEncrypted)
if ($success -ne $true) {
    $($crypt.LastErrorText)
    exit
}

# Make a "-----BEGIN PKCS7-----" ... "-----END PKCS7-----" sandwich...
$sb = New-Object Chilkat.StringBuilder
$sb.AppendLine("-----BEGIN PKCS7-----",$true)
$sb.Append($encryptedStr)
$sb.AppendLine("-----END PKCS7-----",$true)

$outStr = $sb.GetAsString()

$($outStr)

# Sample output:

# -----BEGIN PKCS7-----
# MIICXAYJKoZIhvcNAQcDoIICTTCCAkkCAQAxggH0MIIB8AIBADCBrDCBlzELMAkGA1UEBhMCR0Ix
# GzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMR
# Q09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhlbnRpY2F0
# aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0ECEB6M1ZwZdZU7LrAIdurulmUwOAYJKoZIhvcNAQEHMCug
# DzANBglghkgBZQMEAgEFAKEYMBYGCSqGSIb3DQEBCDAJBgUrDgMCGgUABIIBAK/BZG/iXJ8az7zL
# 8EQ77mc+oDPQ4w1hyytK2ip4djkPVvTfYhcoDQ+G/DBU+urJfrVBi5H9gmpXwYyfKlyUxBVRVEJl
# V/V5QQi4JmNTFbmgWh5tp9zDS98l6A2Va4Zs0Wy/owGLfvwitlxd1dsfVAV2hmBYS24BMpNcty5/
# 0atcKYmSou13G78ztTKdMy1tECgZy8kerMsPdDQbSxEZkT3KpQ8C5uEQqYF3bIVaeZzha/Ywieh/
# tvO0T4aAmeJufwkNdVECmU7kuhnNaVPXknFl7jeibTl6zA/VcJKBKcIYT9FRC7KjdooI8q+jtQ/V
# k6RP4POaowkFg1QWRPEWeqIwTAYJKoZIhvcNAQcBMB0GCWCGSAFlAwQBAgQQEEFQduqeJqXQXzy4
# JpkoDoAgdldJDB9zEkpMpgr5/fR2iLvh5kC6BPfhOYjsawBY4Ok=
# -----END PKCS7-----

# ----------------------------------------------------------------------------------------
# Let's Decrypt the above string.

# Start with what was produced above..
$sb.Clear()
$bCrlf = $true
$sb.AppendLine("-----BEGIN PKCS7-----",$bCrlf)
$sb.AppendLine("MIICXAYJKoZIhvcNAQcDoIICTTCCAkkCAQAxggH0MIIB8AIBADCBrDCBlzELMAkGA1UEBhMCR0Ix",$bCrlf)
$sb.AppendLine("GzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMR",$bCrlf)
$sb.AppendLine("Q09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhlbnRpY2F0",$bCrlf)
$sb.AppendLine("aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0ECEB6M1ZwZdZU7LrAIdurulmUwOAYJKoZIhvcNAQEHMCug",$bCrlf)
$sb.AppendLine("DzANBglghkgBZQMEAgEFAKEYMBYGCSqGSIb3DQEBCDAJBgUrDgMCGgUABIIBAK/BZG/iXJ8az7zL",$bCrlf)
$sb.AppendLine("8EQ77mc+oDPQ4w1hyytK2ip4djkPVvTfYhcoDQ+G/DBU+urJfrVBi5H9gmpXwYyfKlyUxBVRVEJl",$bCrlf)
$sb.AppendLine("V/V5QQi4JmNTFbmgWh5tp9zDS98l6A2Va4Zs0Wy/owGLfvwitlxd1dsfVAV2hmBYS24BMpNcty5/",$bCrlf)
$sb.AppendLine("0atcKYmSou13G78ztTKdMy1tECgZy8kerMsPdDQbSxEZkT3KpQ8C5uEQqYF3bIVaeZzha/Ywieh/",$bCrlf)
$sb.AppendLine("tvO0T4aAmeJufwkNdVECmU7kuhnNaVPXknFl7jeibTl6zA/VcJKBKcIYT9FRC7KjdooI8q+jtQ/V",$bCrlf)
$sb.AppendLine("k6RP4POaowkFg1QWRPEWeqIwTAYJKoZIhvcNAQcBMB0GCWCGSAFlAwQBAgQQEEFQduqeJqXQXzy4",$bCrlf)
$sb.AppendLine("JpkoDoAgdldJDB9zEkpMpgr5/fR2iLvh5kC6BPfhOYjsawBY4Ok=",$bCrlf)
$sb.AppendLine("-----END PKCS7-----",$bCrlf)

$decrypt = New-Object Chilkat.Crypt2
$decrypt.CryptAlgorithm = "pki"

# Use the same cert + private key from the PFX above.
# For decryption, we need the private key.  Given that the certificate was loaded from a PFX,
# we should already have it.
$success = $decrypt.SetDecryptCert($cert)

$decrypt.EncodingMode = "base64"
$decryptedText = $decrypt.DecryptStringENC($sb.GetBetween("-----BEGIN PKCS7-----","-----END PKCS7-----"))

$($decryptedText)