(DataFlex) 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.

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

Use ChilkatAx-9.5.0-win32.pkg

Procedure Test
    Handle hoRsa
    String sPublicKey
    String sPrivateKey
    Boolean iSuccess
    String sPlainText
    Boolean iUsePrivateKey
    String sEncryptedStr1
    String sEncryptedStr2
    Handle hoRsa2
    String sDecryptedStr1
    String sDecryptedStr2

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

    Get Create (RefClass(cComChilkatRsa)) To hoRsa
    If (Not(IsComObjectCreated(hoRsa))) Begin
        Send CreateComObject of hoRsa
    End

    // RSA public key in XML format:
    Move "<RSAPublicKey><Modulus>xxyv1RDPU0MvfFIIa98HppXdcuI7zSu8uIqyGAy/VoxPvxZFX0acajznvjVRHipHbpcO6ryo2LwXUPf89qOqLb3Qd1lfD2ZnH+TQ6MZXNxfFRxTpTUd+tTR4EBYpd2t6kzq8ZRJYLdlviaMQQqUEwR54k7Op5HJYVKUcHIkP1xE=</Modulus><Exponent>AQAB</Exponent></RSAPublicKey>" To sPublicKey

    Move "<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>" To sPrivateKey

    Get ComImportPublicKey Of hoRsa sPublicKey To iSuccess

    // Encrypt a string and return the encrypted data base64-encoded:
    Set ComEncodingMode Of hoRsa To "base64"

    Move "RSA gives different results with each call, weird but OK" To sPlainText

    Move False To iUsePrivateKey
    Get ComEncryptStringENC Of hoRsa sPlainText iUsePrivateKey To sEncryptedStr1
    Showln sEncryptedStr1

    // Do it again. The results are different...
    Get ComEncryptStringENC Of hoRsa sPlainText iUsePrivateKey To sEncryptedStr2
    Showln sEncryptedStr2

    // Now decrypt both strings, and the results are correct
    // in both cases:
    Get Create (RefClass(cComChilkatRsa)) To hoRsa2
    If (Not(IsComObjectCreated(hoRsa2))) Begin
        Send CreateComObject of hoRsa2
    End
    Get ComImportPrivateKey Of hoRsa2 sPrivateKey To iSuccess
    Set ComEncodingMode Of hoRsa2 To "base64"
    Move True To iUsePrivateKey

    Get ComDecryptStringENC Of hoRsa2 sEncryptedStr1 iUsePrivateKey To sDecryptedStr1
    Showln sDecryptedStr1

    Get ComDecryptStringENC Of hoRsa2 sEncryptedStr2 iUsePrivateKey To sDecryptedStr2
    Showln sDecryptedStr2


End_Procedure