1-Wire API for .NET Version 4.00
Public Member Functions | Static Public Attributes | Protected Member Functions

SHADebitUnsigned Class Reference

Inherits com::dalsemi::onewire::application::sha::SHATransaction.

List of all members.

Public Member Functions

 SHADebitUnsigned (SHAiButtonCopr copr)
 SHADebitUnsigned constructor.
 SHADebitUnsigned (SHAiButtonCopr copr, int initialAmount, int debitAmount)
 SHADebitUnsigned constructor.
boolean setupTransactionData (SHAiButtonUser user) throws OneWireException, OneWireIOException
synchronized boolean verifyUser (SHAiButtonUser user) throws OneWireException, OneWireIOException
synchronized boolean verifyTransactionData (SHAiButtonUser user) throws OneWireException, OneWireIOException
synchronized boolean executeTransaction (SHAiButtonUser user, boolean verifySuccess) throws OneWireException, OneWireIOException
synchronized int getParameter (int type)
synchronized boolean setParameter (int type, int param)
synchronized void resetParameters ()

Static Public Attributes

static final int DEBIT_AMOUNT = 0
 Update the amount this transaction will debit.
static final int INITIAL_AMOUNT = 1
 Update the amount for initial account balance.
static final int USER_BALANCE = 2
 Retrieve the amount for user's current balance.

Protected Member Functions

 SHADebitUnsigned ()
 User apps should never call this.

Detailed Description

This class implements an account debit application for unsigned SHA Transactions. Account data is stored on user iButtons with no digital signature (unlike SHADebit which signs the data with a coprocessor iButton).

You may be wondering, "Why use a SHA transaction interface for unsigned account data?" The answer is for increasing transaction times with the DS1961S user iButton. All data writes to the DS1961S require knowledge of the iButton's unique secret, which prevents tampering with the account data. Since a data signature on account data is designed for the same purpose, it is removed from this transaction to remove redundancy and achieve better performance with the DS1961S.

Due to the nature of the DS1961S/DS2432 (i.e. it's designed as a battery-less EEPROM device for 'touch' environments), it is possible that account data could be corrupted if the writing of the data is interrupted. In fact, it is also possible that if the writing of a single bit is interrupted, that bit could become borderline (i.e. right on the line of being a 1 or a 0, such that the 1-Wire I/O logic reads it as a 1 and the SHA engine reads it as a 0) and could be permanently corrupted. As a workaround to problems of this nature, a double-write scheme is used where the length indicates which record is the actual account balance.

The account file consists of the following:

If the length of the account file is 13, then the current record is Record A. If the length of the account file is 21, then the current record is Record B. When updating the button, first the other record is updated (i.e. if Record A is current, then update Record B with the new balance) and write the new data for that record to the button. After verifying that the data was written correctly, the file pointer is the updated to point to the new record. If data corruption occurs at any point in the transaction (and the user doesn't hang around long enough to allow the transaction system a chance to fix it), the next time the user performs a transaction it is possible to discern what the last known good value is.

A typical use case for this class might be as follows:

   OneWireContainer18 coprOWC18 = new OneWireContainer18(adapter,address);
   //COPR.0 is the filename for coprocessor service data
   SHAiButtonCopr copr = new SHAiButtonCopr(coprOWC18,"COPR.0");
   //Initial amount for new users is $100, and debit amount is 50 cents
   SHATransaction trans = new SHADebitUnsigned(copr, 10000, 50);
   OneWireContainer33 owc33 = new OneWireContainer33(adapter, userAddress);
   //The following constructor erases all transaction data from the user and
   //installs the system authentication secret on the user iButton.
   //The second instance of coprocessor is used for write-authorization.  If you're
   //not using the system coprocessor for data signing, it can be re-used for this
   //purpose.
   SHAiButtonUser user = new SHAiButtonUser33(copr, copr, owc33, true, authSecret);
   //creates account data on iButton
   if(trans.setupTransactionData(user))
      System.out.println("Account data installed successfully");
   else
      System.out.println("Account data installation failed");
   //... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
   //verifies authentication response of user iButton from "challenge"
   if(trans.verifyUser(user))
   {
      System.out.println("User Verified Successfully");
      //Checks to see that account balance is greater than zero
      if(trans.verifyTransactionData(user))
      {
         System.out.println("Account Data Verified Successfully");
         //performs the debit and writes the new account balance
         if(trans.executeTransaction(user))
         {
            System.out.println("Account debited.");
            System.out.println("New Balance: " +
               trans.getParameter(SHADebit.USER_BALANCE));
         }
      }
   }
   //... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
   if(trans.getLastError()!=0)
   {
      System.err.println("Error code: " + trans.getLastError());
   }
 

This class makes use of several performance enhancements for TINI. For instance, most methods are synchronized to access instance variable byte arrays rather than creating new byte arrays every time a transaction is performed. This could hurt performance in multi-threaded applications, but the usefulness of having several threads contending to talk to a single iButton is questionable since the methods in com.dalsemi.onewire.adapter.DSPortAdapter beginExclusive(boolean) and endExclusive() should be used.

See also:
SHATransaction
SHAiButtonCopr
SHAiButtonUser
Version:
1.00
Author:
SKH

Constructor & Destructor Documentation

SHADebitUnsigned constructor.

copr is the SHAiButtonCopr that is used to perform this transaction. After saving a reference to the SHA coprocessor, this constructor resets all parameters for this type of transaction to their default values.

Parameters:
coprThe coprocessor used for authentication and data signing in this transaction.
SHADebitUnsigned ( SHAiButtonCopr  copr,
int  initialAmount,
int  debitAmount 
)

SHADebitUnsigned constructor.

copr is the SHAiButtonCopr that is used to perform this transaction. After saving a reference to the SHA coprocessor, this constructor resets all parameters for this type of transaction to their default values.

Parameters:
coprThe coprocessor used for authentication and data signing in this transaction.

Member Function Documentation

synchronized boolean executeTransaction ( SHAiButtonUser  user,
boolean  verifySuccess 
) throws OneWireException, OneWireIOException [virtual]

Performs the unsigned debit, subtracting the debit amount from the user's balance and storing the new, unsigned account data on the user's iButton. The debit amount can be set using transaction.setParameter(SHADebit.DEBIT_AMOUNT, 50), where the value is in units of cents (i.e. for 1 dollar, use 100).

Flow of action:

  • Read the account data from user
  • Extract account balance
  • Assert balance greater than debit amount
  • Debit money from balance
  • Insert the new balance
  • Write the account data to the user

If previous steps have been executed, all "Read" commands on the user are reading from cached data.

Parameters:
userSHAiButtonUser upon which the transaction occurs.
Returns:
true if and only if the user has enough in the account balance to perform the requested debit AND the account data has been written to the button.
See also:
SHAiButtonUser.readAccountData(byte[],int)
SHAiButtonUser.writeAccountData(byte[],int)
getLastError()

Implements SHATransaction.

synchronized int getParameter ( int  type) [virtual]

Retrieves the value of a particular parameter for this debit transaction.

Valid Parameters

Note that the value of SHADebit.USER_BALANCE will be set after calling verifyTransactionData(SHAiButtonUser) and after calling executeTransaction(SHAiButtonUser).

Returns:
The value of the requested parameter.
Exceptions:
IllegalArgumentExceptionif an invalid parameter type is requested.

Implements SHATransaction.

synchronized void resetParameters ( ) [virtual]

Resets all transaction parameters to default values

Implements SHATransaction.

synchronized boolean setParameter ( int  type,
int  param 
) [virtual]

Sets the value of a particular parameter for this debit transaction.

Valid Parameters

Parameters:
typeSpecifies the parameter type (SHADebit.DEBIT_AMOUNT or SHADebit.INITIAL_AMOUNT)
Returns:
true if a valid parameter type was specified and the value of the parameter is positive.
Exceptions:
IllegalArgumentExceptionif an invalid parameter type is requested.

Implements SHATransaction.

boolean setupTransactionData ( SHAiButtonUser  user) throws OneWireException, OneWireIOException [virtual]

Setup account data on a fresh user iButton. Prior to calling setup transaction data, the authentication secret for the iButton should already be setup and a directory entry (as well as at least an empty placeholder file) should exist for the account data. If you constructed the SHAiButtonUser using SHAiButtonUser(SHAiButtonCopr,OneWireContainer18,boolean,byte[]) the secret has been setup for you and you should know call this function. If you try to install the authentication secret after creating the account data, you will destroy all account data on the iButton.

You can set the value of the intial account balance by calling transaction.setParameter(SHADebit.INITIAL_AMOUNT,10000) where the value of the units is in cents (i.e. 10000 = $100).

Flow of action:

  • Generate generic account page
  • Insert the initial balance into account data
  • Insert the (constant) digital signature
  • Write account data page to iButton
Parameters:
userSHAiButtonUser upon which the transaction occurs.
Returns:
trueif and only if the signature is successfully created by the coprocessor AND the data is successfully written to the user iButton.
See also:
SHAiButtonUser.writeAccountData(byte[],int)
getLastError()

Implements SHATransaction.

synchronized boolean verifyTransactionData ( SHAiButtonUser  user) throws OneWireException, OneWireIOException [virtual]

Verifies user's account data. Account data is "verified" if and only if the account balance is greater than zero. No digital signature is checked by this transaction.

Flow of action:

  • Read the account data from user
  • Extract account balance
  • Debit money from balance
  • Insert the new balance
  • Write the account data to the user

If previous steps have been executed, all "Read" commands on the user are reading from cached data.

Parameters:
userSHAiButtonUser upon which the transaction occurs.
Returns:
true if and only if the account balance is greater than zero.
See also:
SHAiButtonUser.readAccountData(byte[],int)
getLastError()

Implements SHATransaction.

synchronized boolean verifyUser ( SHAiButtonUser  user) throws OneWireException, OneWireIOException [virtual]

Verifies user's authentication response. User is "authenticated" if and only if the digital signature generated the user iButton matches the digital signature generated by the coprocessor after the user's unique secret has been recreated on the coprocessor.

Flow of action:

  • Generate 3-byte "challenge" on coprocessor
  • Write challenge to scratchpad of user
  • Read account data page with signature
  • Attempt to match user's signature with the coprocessor
Parameters:
userSHAiButtonUser upon which the transaction occurs.
See also:
SHAiButtonCopr.generateChallenge(int,byte[],int)
SHAiButtonCopr.verifyAuthentication(byte[],byte[],byte[],byte[],byte)
SHAiButtonUser.readAccountData(byte[],int,byte[],int,byte[],int)
getLastError()

Implements SHATransaction.


The documentation for this class was generated from the following file: