(PowerBuilder) RSA Encryption -- Same Key Different Results

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.

*** The reason this occurs is that RSA encryption uses PKCS1 v1.5 padding, and this padding scheme uses random bytes. It is random bytes in the padding that causes the result to be different each time.

Note: This example requires Chilkat v11.0.0 or greater.

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

integer li_rc
integer li_Success
oleobject loo_Rsa
string ls_PubKeyXml
string ls_PrivKeyXml
oleobject loo_PubKey
oleobject loo_PrivKey
string ls_PlainText
integer li_UsePrivateKey
string ls_EncryptedStr1
string ls_EncryptedStr2
oleobject loo_Rsa2
string ls_DecryptedStr1
string ls_DecryptedStr2

li_Success = 0

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

loo_Rsa = create oleobject
li_rc = loo_Rsa.ConnectToNewObject("Chilkat.Rsa")
if li_rc < 0 then
    destroy loo_Rsa
    MessageBox("Error","Connecting to COM object failed")
    return
end if

ls_PubKeyXml = "<RSAPublicKey><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent></RSAPublicKey>"

ls_PrivKeyXml = "<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>"

loo_PubKey = create oleobject
li_rc = loo_PubKey.ConnectToNewObject("Chilkat.PublicKey")

li_Success = loo_PubKey.LoadFromString(ls_PubKeyXml)
if li_Success = 0 then
    Write-Debug loo_PubKey.LastErrorText
    destroy loo_Rsa
    destroy loo_PubKey
    return
end if

loo_PrivKey = create oleobject
li_rc = loo_PrivKey.ConnectToNewObject("Chilkat.PrivateKey")

li_Success = loo_PrivKey.LoadXml(ls_PrivKeyXml)
if li_Success = 0 then
    Write-Debug loo_PrivKey.LastErrorText
    destroy loo_Rsa
    destroy loo_PubKey
    destroy loo_PrivKey
    return
end if

li_Success = loo_Rsa.UsePublicKey(loo_PubKey)
if li_Success = 0 then
    Write-Debug loo_Rsa.LastErrorText
    destroy loo_Rsa
    destroy loo_PubKey
    destroy loo_PrivKey
    return
end if

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

ls_PlainText = "RSA gives different results with each call, weird but OK"

li_UsePrivateKey = 0
ls_EncryptedStr1 = loo_Rsa.EncryptStringENC(ls_PlainText,li_UsePrivateKey)
Write-Debug ls_EncryptedStr1

// Do it again. The results are different...
ls_EncryptedStr2 = loo_Rsa.EncryptStringENC(ls_PlainText,li_UsePrivateKey)
Write-Debug ls_EncryptedStr2

// Now decrypt both strings, and the results are correct
// in both cases:
loo_Rsa2 = create oleobject
li_rc = loo_Rsa2.ConnectToNewObject("Chilkat.Rsa")

li_Success = loo_Rsa2.UsePrivateKey(loo_PrivKey)
if li_Success = 0 then
    Write-Debug loo_Rsa.LastErrorText
    destroy loo_Rsa
    destroy loo_PubKey
    destroy loo_PrivKey
    destroy loo_Rsa2
    return
end if

loo_Rsa2.EncodingMode = "base64"
li_UsePrivateKey = 1

ls_DecryptedStr1 = loo_Rsa2.DecryptStringENC(ls_EncryptedStr1,li_UsePrivateKey)
Write-Debug ls_DecryptedStr1

ls_DecryptedStr2 = loo_Rsa2.DecryptStringENC(ls_EncryptedStr2,li_UsePrivateKey)
Write-Debug ls_DecryptedStr2


destroy loo_Rsa
destroy loo_PubKey
destroy loo_PrivKey
destroy loo_Rsa2