(Xojo Plugin) 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 Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

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

Dim crypt As New 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).
Dim cert1 As New Chilkat.Cert
Dim success As Boolean
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

Dim cert2 As New Chilkat.Cert
success = cert2.LoadFromFile("qa_data/user2/cert_user2.pem")
crypt.AddEncryptCert cert2

Dim cert3 As New 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...
Dim fileData As New 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 <> True) Then
    System.DebugLog(crypt.LastErrorText)
    Return
End If

//  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"

System.DebugLog("OK.")