RSA Encryption -- Same Key Different Results

Download Chilkat RSA ActiveX

The RSA encryption algorithm produces different results for each call, even when encrypting the same data with the same key. Decryption however, will produce the correct results. This example demonstrates.

Dim rsa As New ChilkatRsa

Dim success As Long
success = rsa.UnlockComponent("Anything for 30-day trial")
If (success <> 1) Then
    MsgBox "RSA component unlock failed"
    Exit Sub
End If

'  RSA public key in XML format:
Dim publicKey As String
publicKey = "<RSAKeyValue><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>"

Dim privateKey As String
privateKey = "<RSAKeyValue><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent><P>4cpW9fvG99Jsz8/AO7PDHTl+pPRAglksrR2kClLV2g9DEeFe/bvmCxLUgMCJ+0eGQ1zA6aA7McKr13zTQ7jKpQ==</P><Q>4cCS/kFlq/P1ExF37Fkh4pCodOEGutepLEG7Q/KljT3ZGlAY+2l8fGu4f+hrkUuGoFl7NOMaJflULoPIgQaq/Q==</Q><DP>lkjcSsvzqh3YKRXJiLNkyf3rypV8noYGU4+oEOsDxilkZfFRDafUPUiiQrRk4ui/d/SzvozU+ZDuWfaOk8PatQ==</DP><DQ>SYCD25i7W8Mwdibn3uIecEAdOQDTSh5RjIFSUYs9b8FFYJXXrHPp/jCsf6jS7RmkGa1Iui1/JAIL8KEjtS7QmQ==</DQ><InverseQ>EDAJa3TpNdPQ3GIdBpnTgFTQY5A60DcszsUW/iCYoXQdPVJ9BLBxVTe9jiLzGuNuzLkVBwQlCy0Bf84hACRV9A==</InverseQ><D>cMFdDYKkddlRNczaugOmOH8b1egpx2liSPs6GYZ2gFObAXJiPK8m+r6c2ckls7hrlUP0DZhi4cG6Tn7xANb0Ek17P7QquVhQYOmFy/YHzm+IJbcwwq7pJHhZBhtcjyXqfUZ+BADGE//GQbrSVwVltpOj5KcxG88NAprLn2MMxfE=</D></RSAKeyValue>"

rsa.ImportPublicKey publicKey

'  Encrypt a string and return the encrypted data base64-encoded:
rsa.EncodingMode = "base64"

Dim plainText As String
plainText = "RSA gives different results with each call, weird but OK"

Dim usePrivateKey As Long
usePrivateKey = 0
Dim encryptedStr1 As String
encryptedStr1 = rsa.EncryptStringENC(plainText,usePrivateKey)
Text1.Text = Text1.Text & encryptedStr1 & vbCrLf
Text1.Refresh

'  Do it again. The results are different...
Dim encryptedStr2 As String
encryptedStr2 = rsa.EncryptStringENC(plainText,usePrivateKey)
Text1.Text = Text1.Text & encryptedStr2 & vbCrLf
Text1.Refresh

'  Now decrypt both strings, and the results are correct
'  in both cases:
Dim rsa2 As New ChilkatRsa
rsa2.ImportPrivateKey privateKey
rsa2.EncodingMode = "base64"
usePrivateKey = 1

Dim decryptedStr1 As String
decryptedStr1 = rsa2.DecryptStringENC(encryptedStr1,usePrivateKey)
Text1.Text = Text1.Text & decryptedStr1 & vbCrLf
Text1.Refresh

Dim decryptedStr2 As String
decryptedStr2 = rsa2.DecryptStringENC(encryptedStr2,usePrivateKey)
Text1.Text = Text1.Text & decryptedStr2 & vbCrLf
Text1.Refresh