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Class ajanta.agent.AppendOnlyContainer 

java.lang.Object
   |
   +----ajanta.agent.AppendOnlyContainer
public class AppendOnlyContainer
extends Object
The read-only container mechanism is limited in utility to those parts of the state that remain constant throughout the agent's travels. In some situations, the agent needs to collect data from the sites it visits, but also needs to prevent any subsequent modification of the data. This could be termed as write-once data, although more generally, it could be modified any number of times until the agent decides that it should not be modifiable any further. More generally, agents may need append-only logs as part of their state. An append-only log, as the name implies, can only be appended to, i.e., entries in the log cannot be deleted or modified. When a data object needs to be "frozen", it can be inserted into such an append-only log. If secrecy is also needed the item can be encrypted with the agent's public key before it is stored in the log.

See Also:
ReadOnlyContainer

Variable Index

o objs
o signers
o signs

Constructor Index

o AppendOnlyContainer(EGPublicKey, int)
Constructor requires the agent's creator to supply the Elgamal public key of the agent which will be used to sign the random number ( nonce) for initialization.

Method Index

o checkIn(Object, byte[], URN)
checkIn method is used to insert an object "X" (of any type) into an AppendOnlyContainer.
o verify(EGPrivateKey)
When the agent returns home, the owner can use the verify method to ensure that the AppendOnlyContainer has not been tampered with.

Variables

o objs 
 public Vector objs
o signs 
 public Vector signs
o signers 
 public Vector signers

Constructors

o AppendOnlyContainer 
 public AppendOnlyContainer(EGPublicKey key,
                            int random)
Constructor requires the agent's creator to supply the Elgamal public key of the agent which will be used to sign the random number ( nonce) for initialization. This nonce is not known to any server other than the agent's home site, and must be kept secret.

Parameters:
key - Agent's Elgamal public key to be used for signing
random - any random integer number

Methods

o checkIn 
 public void checkIn(Object X,
                     byte sig[],
                     URN server)
checkIn method is used to insert an object "X" (of any type) into an AppendOnlyContainer. The check-in procedure requests the current server to sign the object using its own private key.

Parameters:
X - object to be inserted
sig - signed byte array
server - URN of the current server
o verify 
 public int verify(EGPrivateKey privkey) throws SecurityException
When the agent returns home, the owner can use the verify method to ensure that the AppendOnlyContainer has not been tampered with.

Parameters:
key - The Elgamal private key for the agent.
Returns:
It returns a number and this number should be compared with the original random number passed to the constructor (which must therefore,be stored by the agent's creator for later verification). If it does not match, a security exception can be thrown. One limitation of this scheme is that the verification process requires the agent's private key, and can thus only be done by the agent's home site (or some other site trusted by its owner). 
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