PureBasic

Demonstrate RSA Encrypt/Decrypt using BinData

See more RSA Examples

Demonstrates how to RSA encrypt and decrypt data contained in a Chilkat BinData object. PureBasic

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

Procedure ChilkatExample()

    success.i = 0

    ; 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 = 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::ckUsePublicKey(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

    ; Create some binary data to encrypt.
    bd.i = CkBinData::ckCreate()
    If bd.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    i.i = 0
    For i = 0 To 49
        CkBinData::ckAppendByte(bd,i)
    Next

    ; Show the bytes to be encrypted in hex format:
    Debug "To be encrypted: " + CkBinData::ckGetEncoded(bd,"hex")

    ; To be encrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031

    ; RSA encrypt the contents of the bd, replacing the contents with the RSA encrypted data.
    CkRsa::ckEncryptBd(rsa,bd,0)

    ; Now it is encrypted.
    Debug "Encrypted size = " + Str(CkBinData::ckNumBytes(bd))
    Debug CkBinData::ckGetEncoded(bd,"hex")

    ; Encrypted size = 256
    ; 749ED9D0A8767C06C09AD9697F654F86B145F966722F9714902C4175BDBD02E68984ECF111D4D461
    ; EDB4A8E677D399D19CCA60F35C6DE9972F4262880FE9D77DB75915393E8E7DB80AAB5E383013FAEB
    ; 60C77D1E6FECC9A7C8426976416C6218FE7DA998EE063CE709E79C240F8625F4A56A0A33AFD63F7A
    ; BA26F2A692B42E878C53B78602C725FE63FF961A46A2B9D436E5E3D9D64AE3F1D1F5AD5F5B47FCD69
    ; 447306B77F2FD6D766CCAA1A110A3371586B43DF0D7FFE2220D1B305CF9371AC342F849FB0C90CD99E
    ; C176928D877FE1C0DE1A7CB6EB824FEC7E1DCF90EF2C6BA9F1DFD3EBFBE89C51AF074DC6AE02E544A78
    ; 5018C36D3D48B2EF5202AF61AC

    ; ------------------------------------------------------------------------------------------------------------------------
    ; 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)
        CkBinData::ckDispose(bd)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

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

    ; Decrypt
    success = CkRsa::ckDecryptBd(rsa,bd,1)
    If success = 0
        Debug CkRsa::ckLastErrorText(rsa)
        CkPublicKey::ckDispose(pubKey)
        CkRsa::ckDispose(rsa)
        CkBinData::ckDispose(bd)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    ; Examine the contents of bd to see if it now contains the unencrypted original data.
    Debug "Decrypted: " + CkBinData::ckGetEncoded(bd,"hex")

    ; Decrypted: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F3031


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


    ProcedureReturn
EndProcedure