(VB.NET) openssl enc decrypt

Demonstrates how to decrypt a file that was encrypted using "openssl enc".

This example shows how to decrypt what was created using this openssl command:

openssl enc -e -aes-256-cbc -in hamlet.xml -out hamlet.enc -pass file:./secret.txt

This example shows how to do this:

openssl enc -d -aes-256-cbc -in hamlet.enc -out hamlet_dec.xml -pass file:./secret.txt

Note: This example requires Chilkat v9.5.0.71 or later.

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

Dim crypt As New Chilkat.Crypt2

' Use aes-256-cbc
crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "cbc"
crypt.KeyLength = 256

' We'll need to set the hash algorithm to either MD5 or SHA256.
' openssl version 1.0.* or earlier used MD5 by default
' openssl version 1.1.* uses SHA-256 for the password to secret key derivation.

' For example, if openssl 1.1.0 was used, we should do this:
crypt.HashAlgorithm = "sha256"

' This example assumes openssl 1.0.2 was used to encrypt what we're now decrypting:
crypt.HashAlgorithm = "md5"

' The openssl command we are duplicating is:
' 
'    openssl enc -d -aes-256-cbc -in hamlet.enc -out hamlet_dec.xml -pass file:./secret.txt
' 
' The file secret.txt contains the word "secret".  We could write code to load the contents
' of secret.txt, but instead we'll just do this:
crypt.SetSecretKeyViaPassword("secret")

' Load the file to be decrypted.
Dim fileData As New Chilkat.BinData
Dim success As Boolean = fileData.LoadFile("qa_data/openssl_enc/hamlet.enc")

' Decrypt
success = crypt.DecryptBd(fileData)

' Save the decrypted output.
success = fileData.WriteFile("qa_output/hamlet_dec.xml")

Debug.WriteLine("success = " & success)