(Visual Basic 6.0) RSA Encrypt RSA/ECB/OAEPWithSHA1AndMGF1Padding

Demonstrates how to RSA encrypt using RSA/ECB/OAEPWithSHA1AndMGF1Padding. Also demonstrates RSA/ECB/OAEPWithSHA-256AndMGF1Padding. Both of these terms are from Java's JCE. Note: In this context, "ECB" doesn't actually mean anything. It's a symmetric cipher mode that doesn't apply (or make sense) in this context.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

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

Dim rsa As New ChilkatRsa

' First load a public key object with a public key.
' In this case, we'll load it from a file.
Dim pubkey As New PublicKey
Dim success As Long
success = pubkey.LoadFromFile("qa_data/pem/rsa_public.pem")
If (success <> 1) Then
    Debug.Print pubkey.LastErrorText
    Exit Sub
End If

' RSA encryption is limited to small amounts of data. The limit
' is typically a few hundred bytes and is based on the key size and
' padding (OAEP vs. PKCS1_5).  RSA encryption is typically used for
' encrypting hashes or symmetric (bulk encryption algorithm) secret keys.
Dim plainText As String
plainText = "Time is an illusion. Lunchtime doubly so."

' Import the public key to be used for encrypting.
success = rsa.ImportPublicKeyObj(pubkey)

' To get OAEP padding, set the OaepPadding property:
rsa.OaepPadding = 1

' To use SHA1 or SHA-256, set the OaepHash property
rsa.OaepHash = "sha256"
' for SHA1 --
rsa.OaepHash = "sha1"

' Indicate we'll want hex output
rsa.EncodingMode = "hex"

' Encrypt..
Dim usePrivateKey As Long
usePrivateKey = 0
Dim encryptedStr As String
encryptedStr = rsa.EncryptStringENC(plainText,usePrivateKey)
Debug.Print encryptedStr

' -------------------------------------------------
' Now decrypt with the matching private key.
Dim rsa2 As New ChilkatRsa

Dim privKey As New PrivateKey
success = privKey.LoadEncryptedPem("qa_data/pem/rsa_passwd.pem","passwd")
If (success <> 1) Then
    Debug.Print privKey.LastErrorText
    Exit Sub
End If

success = rsa2.ImportPrivateKeyObj(privKey)

' Make sure we have the same settings used for encryption.
rsa2.OaepPadding = 1
rsa2.EncodingMode = "hex"
rsa2.OaepHash = "sha1"

Dim originalStr As String
originalStr = rsa2.DecryptStringENC(encryptedStr,1)

Debug.Print originalStr