(VB.NET) 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 Framework Chilkat for .NET Core

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


Dim crypt As New 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.)
Dim cert As New Chilkat.Cert
Dim success As Boolean = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
If (success <> True) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


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

Dim toBeEncrypted As String = "This string is to be encrypted."

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

Dim encryptedStr As String = crypt.EncryptStringENC(toBeEncrypted)
If (success <> True) Then
    Debug.WriteLine(crypt.LastErrorText)
    Exit Sub
End If


' Make a "-----BEGIN PKCS7-----" ... "-----END PKCS7-----" sandwich...
Dim sb As New Chilkat.StringBuilder
sb.AppendLine("-----BEGIN PKCS7-----",True)
sb.Append(encryptedStr)
sb.AppendLine("-----END PKCS7-----",True)

Dim outStr As String = sb.GetAsString()

Debug.WriteLine(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()
Dim bCrlf As Boolean = 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)


Dim decrypt As New 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"
Dim decryptedText As String = decrypt.DecryptStringENC(sb.GetBetween("-----BEGIN PKCS7-----","-----END PKCS7-----"))

Debug.WriteLine(decryptedText)