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.

Download Chilkat RSA Public-Key Encryption ActiveX

LOCAL loRsa
LOCAL lnSuccess
LOCAL lcPublicKey
LOCAL lcPrivateKey
LOCAL lcPlainText
LOCAL lnUsePrivateKey
LOCAL lcEncryptedStr1
LOCAL lcEncryptedStr2
LOCAL loRsa2
LOCAL lcDecryptedStr1
LOCAL lcDecryptedStr2

loRsa = CreateObject('Chilkat.Rsa')

lnSuccess = loRsa.UnlockComponent("Anything for 30-day trial")
IF (lnSuccess <> 1) THEN
    =MESSAGEBOX("RSA component unlock failed")
    QUIT
ENDIF

*  RSA public key in XML format:

lcPublicKey = "<RSAKeyValue><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>"

lcPrivateKey = "<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>"

loRsa.ImportPublicKey(lcPublicKey)

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

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

lnUsePrivateKey = 0

lcEncryptedStr1 = loRsa.EncryptStringENC(lcPlainText,lnUsePrivateKey)
? lcEncryptedStr1

*  Do it again. The results are different...

lcEncryptedStr2 = loRsa.EncryptStringENC(lcPlainText,lnUsePrivateKey)
? lcEncryptedStr2

*  Now decrypt both strings, and the results are correct
*  in both cases:
loRsa2 = CreateObject('Chilkat.Rsa')
loRsa2.ImportPrivateKey(lcPrivateKey)
loRsa2.EncodingMode = "base64"
lnUsePrivateKey = 1

lcDecryptedStr1 = loRsa2.DecryptStringENC(lcEncryptedStr1,lnUsePrivateKey)
? lcDecryptedStr1

lcDecryptedStr2 = loRsa2.DecryptStringENC(lcEncryptedStr2,lnUsePrivateKey)
? lcDecryptedStr2