(PureBasic) RSA Encrypt String to Encoded Result and Reverse

See more RSA Examples

Demonstrates how to RSA encrypt a string to a base64 encoded result, and the reverse.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkPublicKey.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkRsa.pb"

Procedure ChilkatExample()

    ; The RSA public key is used for encryption, and the private key for decryption.

    ; The public key's role is to make encryption accessible to anyone while ensuring that
    ; only the private key holder can decrypt the messages.
    ; The public key is designed to be widely distributed so anyone can use it to encrypt messages
    ; intended for the owner of the private key.

    ; Load our 2048-bit RSA public key.
    pubKey.i = CkPublicKey::ckCreate()
    If pubKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; In all Chilkat methods expecting a path, you pass either absolute or relative paths.
    success.i = CkPublicKey::ckLoadFromFile(pubKey,"rsaKeys/myTestRsaPublic.pem")
    If success = 0
        Debug CkPublicKey::ckLastErrorText(pubKey)
        CkPublicKey::ckDispose(pubKey)
        ProcedureReturn
    EndIf

    rsa.i = CkRsa::ckCreate()
    If rsa.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Tell RSA to use the public key.
    CkRsa::ckImportPublicKeyObj(rsa,pubKey)

    ; RSA encryption is for small amounts of data, on the order of 200 bytes or less.
    ; The maximum number of bytes that can be RSA encrypted depends
    ; on the RSA key size and padding scheme (OAEP padding vs PKCS#1 v1.5 padding).
    ; For specific limits, see: RSA Encryption Maximum Number of Bytes

    ; Encrypt the utf-8 byte representation of the string.
    CkRsa::setCkCharset(rsa, "utf-8")
    CkRsa::setCkEncodingMode(rsa, "base64")

    ; Be Careful when Using non-us-ascii String Literals in Source Code
    encryptedB64.s = CkRsa::ckEncryptStringENC(rsa,"Élève français dîne à côté d’un café où l’on sert déjà du gâteau au chocolat et des éclairs délicieux",0)

    ; ------------------------------------------------------------------------------------------------------------------------
    ; Let's decrypt, which requires the matching private key...

    ; Load the matching 2048-bit RSA private key.
    privKey.i = CkPrivateKey::ckCreate()
    If privKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    password.s = "secret"
    success = CkPrivateKey::ckLoadAnyFormatFile(privKey,"rsaKeys/myTestRsaPrivate.pem",password)
    If success = 0
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkPublicKey::ckDispose(pubKey)
        CkRsa::ckDispose(rsa)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    ; Tell the RSA object to use the private key.
    CkRsa::ckImportPrivateKeyObj(rsa,privKey)

    ; Indicate that after decrypting the resultant decrypted bytes contains the utf-8 byte representation of the text.
    CkRsa::setCkCharset(rsa, "utf-8")
    CkRsa::setCkEncodingMode(rsa, "base64")
    originalText.s = CkRsa::ckDecryptStringENC(rsa,encryptedB64,1)
    If success = 0
        Debug CkRsa::ckLastErrorText(rsa)
        CkPublicKey::ckDispose(pubKey)
        CkRsa::ckDispose(rsa)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    Debug "Original text = " + originalText
    Debug "Success."


    CkPublicKey::ckDispose(pubKey)
    CkRsa::ckDispose(rsa)
    CkPrivateKey::ckDispose(privKey)


    ProcedureReturn
EndProcedure