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java.lang.Object
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+--com.dalsemi.onewire.application.sha.SHATransaction
|
+--com.dalsemi.onewire.application.sha.SHADebitUnsigned
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.
SHATransaction,
SHAiButtonCopr,
SHAiButtonUser| Field Summary | |
static int |
DEBIT_AMOUNT
Update the amount this transaction will debit |
static int |
INITIAL_AMOUNT
Update the amount for initial account balance |
static int |
USER_BALANCE
Retrieve the amount for user's current balance |
| Fields inherited from class com.dalsemi.onewire.application.sha.SHATransaction |
COPR_BIND_SECRET_FAILED, COPR_COMPUTE_CHALLENGE_FAILED, COPR_WRITE_DATAPAGE_FAILED, COPR_WRITE_SCRATCHPAD_FAILED, COPROCESSOR_FAILURE, MATCH_SCRATCHPAD_FAILED, NO_ERROR, SHA_FUNCTION_FAILED, USER_BAD_ACCOUNT_DATA, USER_DATA_NOT_UPDATED, USER_READ_AUTH_FAILED, USER_WRITE_DATA_FAILED |
| Constructor Summary | |
SHADebitUnsigned(SHAiButtonCopr copr)
SHADebitUnsigned constructor. |
|
SHADebitUnsigned(SHAiButtonCopr copr,
int initialAmount,
int debitAmount)
SHADebitUnsigned constructor. |
|
| Method Summary | |
boolean |
executeTransaction(SHAiButtonUser user,
boolean verifySuccess)
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. |
int |
getParameter(int type)
Retrieves the value of a particular parameter for this debit transaction. |
void |
resetParameters()
Resets all transaction parameters to default values |
boolean |
setParameter(int type,
int param)
Sets the value of a particular parameter for this debit transaction. |
boolean |
setupTransactionData(SHAiButtonUser user)
Setup account data on a fresh user iButton. |
boolean |
verifyTransactionData(SHAiButtonUser user)
Verifies user's account data. |
boolean |
verifyUser(SHAiButtonUser user)
Verifies user's authentication response. |
| Methods inherited from class com.dalsemi.onewire.application.sha.SHATransaction |
getLastCoprError, getLastError |
| Methods inherited from class java.lang.Object |
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
public static final int DEBIT_AMOUNT
public static final int INITIAL_AMOUNT
public static final int USER_BALANCE
| Constructor Detail |
public SHADebitUnsigned(SHAiButtonCopr copr)
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.copr - The coprocessor used for authentication and data
signing in this transaction.
public SHADebitUnsigned(SHAiButtonCopr copr,
int initialAmount,
int debitAmount)
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.copr - The coprocessor used for authentication and data
signing in this transaction.| Method Detail |
public boolean setupTransactionData(SHAiButtonUser user)
throws OneWireException,
OneWireIOException
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:
setupTransactionData in class SHATransactionuser - SHAiButtonUser upon which the transaction occurs.trueif and only if the signature is
successfully created by the coprocessor AND the data is
successfully written to the user iButton.SHAiButtonUser.writeAccountData(byte[],int),
SHATransaction.getLastError()
public boolean verifyUser(SHAiButtonUser user)
throws OneWireException,
OneWireIOException
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:
verifyUser in class SHATransactionuser - SHAiButtonUser upon which the transaction occurs.SHAiButtonCopr.generateChallenge(int,byte[],int),
SHAiButtonCopr.verifyAuthentication(byte[],byte[],byte[],byte[],byte),
SHAiButtonUser.readAccountData(byte[],int,byte[],int,byte[],int),
SHATransaction.getLastError()
public boolean verifyTransactionData(SHAiButtonUser user)
throws OneWireException,
OneWireIOException
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:
If previous steps have been executed, all "Read" commands on the user are reading from cached data.
verifyTransactionData in class SHATransactionuser - SHAiButtonUser upon which the transaction occurs.true if and only if the account balance is
greater than zero.SHAiButtonUser.readAccountData(byte[],int),
SHATransaction.getLastError()
public boolean executeTransaction(SHAiButtonUser user,
boolean verifySuccess)
throws OneWireException,
OneWireIOException
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:
If previous steps have been executed, all "Read" commands on the user are reading from cached data.
executeTransaction in class SHATransactionuser - SHAiButtonUser upon which the transaction occurs.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.SHAiButtonUser.readAccountData(byte[],int),
SHAiButtonUser.writeAccountData(byte[],int),
SHATransaction.getLastError()public int getParameter(int type)
Retrieves the value of a particular parameter for this debit transaction.
Valid Parameters
SHADebit.DEBIT_AMOUNTSHADebit.INITIAL_AMOUNTSHADebit.USER_BALANCENote that the value of SHADebit.USER_BALANCE will
be set after calling verifyTransactionData(SHAiButtonUser)
and after calling executeTransaction(SHAiButtonUser).
getParameter in class SHATransactionIllegalArgumentException - if an invalid parameter type
is requested.
public boolean setParameter(int type,
int param)
Sets the value of a particular parameter for this debit transaction.
Valid Parameters
SHADebit.DEBIT_AMOUNTSHADebit.INITIAL_AMOUNTsetParameter in class SHATransactiontype - Specifies the parameter type (SHADebit.DEBIT_AMOUNT or
SHADebit.INITIAL_AMOUNT)IllegalArgumentException - if an invalid parameter type
is requested.public void resetParameters()
Resets all transaction parameters to default values
resetParameters in class SHATransaction
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