(Classic ASP) 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 ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

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

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Crypt2")
set crypt = Server.CreateObject("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).
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Cert")
set cert1 = Server.CreateObject("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

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Cert")
set cert2 = Server.CreateObject("Chilkat.Cert")
success = cert2.LoadFromFile("qa_data/user2/cert_user2.pem")
crypt.AddEncryptCert cert2

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Cert")
set cert3 = Server.CreateObject("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 = 1

' Load the file to be encrypted...
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.BinData")
set fileData = Server.CreateObject("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 <> 1) Then
    Response.Write "<pre>" & Server.HTMLEncode( crypt.LastErrorText) & "</pre>"
    Response.End
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"

Response.Write "<pre>" & Server.HTMLEncode( "OK.") & "</pre>"

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