(PureBasic) RSA Encrypt RSA/ECB/OAEPWithSHA1AndMGF1Padding

Demonstrates how to RSA encrypt using RSA/ECB/OAEPWithSHA1AndMGF1Padding. Also demonstrates RSA/ECB/OAEPWithSHA-256AndMGF1Padding. Both of these terms are from Java's JCE. Note: In this context, "ECB" doesn't actually mean anything. It's a symmetric cipher mode that doesn't apply (or make sense) in this context.

Chilkat PureBasic Module Download Chilkat PureBasic Module

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

Procedure ChilkatExample()

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

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

    ; First load a public key object with a public key.
    ; In this case, we'll load it from a file.
    pubkey.i = CkPublicKey::ckCreate()
    If pubkey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkPublicKey::ckLoadFromFile(pubkey,"qa_data/pem/rsa_public.pem")
    If success <> 1
        Debug CkPublicKey::ckLastErrorText(pubkey)
        CkRsa::ckDispose(rsa)
        CkPublicKey::ckDispose(pubkey)
        ProcedureReturn
    EndIf

    ; RSA encryption is limited to small amounts of data. The limit
    ; is typically a few hundred bytes and is based on the key size and
    ; padding (OAEP vs. PKCS1_5).  RSA encryption is typically used for
    ; encrypting hashes or symmetric (bulk encryption algorithm) secret keys.
    plainText.s = "Time is an illusion. Lunchtime doubly so."

    ; Import the public key to be used for encrypting.
    success = CkRsa::ckImportPublicKeyObj(rsa,pubkey)

    ; To get OAEP padding, set the OaepPadding property:
    CkRsa::setCkOaepPadding(rsa, 1)

    ; To use SHA1 or SHA-256, set the OaepHash property
    CkRsa::setCkOaepHash(rsa, "sha256")
    ; for SHA1 --
    CkRsa::setCkOaepHash(rsa, "sha1")

    ; Indicate we'll want hex output
    CkRsa::setCkEncodingMode(rsa, "hex")

    ; Encrypt..
    usePrivateKey.i = 0
    encryptedStr.s = CkRsa::ckEncryptStringENC(rsa,plainText,usePrivateKey)
    Debug encryptedStr

    ; -------------------------------------------------
    ; Now decrypt with the matching private key.
    rsa2.i = CkRsa::ckCreate()
    If rsa2.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

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

    success = CkPrivateKey::ckLoadEncryptedPem(privKey,"qa_data/pem/rsa_passwd.pem","passwd")
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkRsa::ckDispose(rsa)
        CkPublicKey::ckDispose(pubkey)
        CkRsa::ckDispose(rsa2)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    success = CkRsa::ckImportPrivateKeyObj(rsa2,privKey)

    ; Make sure we have the same settings used for encryption.
    CkRsa::setCkOaepPadding(rsa2, 1)
    CkRsa::setCkEncodingMode(rsa2, "hex")
    CkRsa::setCkOaepHash(rsa2, "sha1")

    originalStr.s = CkRsa::ckDecryptStringENC(rsa2,encryptedStr,1)

    Debug originalStr


    CkRsa::ckDispose(rsa)
    CkPublicKey::ckDispose(pubkey)
    CkRsa::ckDispose(rsa2)
    CkPrivateKey::ckDispose(privKey)


    ProcedureReturn
EndProcedure