```
public class POEExtraction
extends Object
```
5.6.2.3 POE extraction 5.6.2.3.1 Description This building block derives POEs from a given time-stamp. Assumptions: - The time-stamp validation has returned PASSED. - The cryptographic hash function used in the time-stamp (messageImprint.hashAlgorithm) is considered reliable at current time or, if this is not the case, a PoE for that time-stamp exists for a time when the hash function has still been considered reliable. In the simple case, a time-stamp gives a POE for each data item protected by the time-stamp at the generation date/time of the token. EXAMPLE: A time-stamp on the signature value gives a POE of the signature value at the generation date/time of the time-stamp. A time-stamp can also give an indirect POE when it is computed on the hash value of some data instead of the data itself. A POE for DATA at T1 can be derived from the time-stamp: - If there is a POE for h(DATA) at a date T1,where h is a cryptographic hash function and DATA is some data (e.g. a certificate), - if h is asserted in the cryptographic constraints to be trusted until at least a date T after T1; and - if there is a POE for DATA at a date T after T1.

Modifier and Type	Method	Description
`void`	`addSignaturePOE(SignatureWrapper signature, XmlProofOfExistence proofOfExistence)`
`void`	`collectAllPOE(DiagnosticData diagnosticData)`
`void`	`extractPOE(TimestampWrapper timestamp)`
`XmlProofOfExistence`	`getLowestPOE(String tokenId, Date controlTime)`
`Date`	`getLowestPOETime(String tokenId, Date controlTime)`
`void`	`init(DiagnosticData diagnosticData, XmlProofOfExistence proofOfExistence)`
`boolean`	`isPOEExists(String tokenId, Date controlTime)`	Returns true if there is a POE exists for a given id at (or before) the control time.

public void init(DiagnosticData diagnosticData,
                 XmlProofOfExistence proofOfExistence)

public void collectAllPOE(DiagnosticData diagnosticData)

public void extractPOE(TimestampWrapper timestamp)

public void addSignaturePOE(SignatureWrapper signature,
                            XmlProofOfExistence proofOfExistence)

public boolean isPOEExists(String tokenId,
                           Date controlTime)

Returns true if there is a POE exists for a given id at (or before) the control time.

public Date getLowestPOETime(String tokenId,
                             Date controlTime)

public XmlProofOfExistence getLowestPOE(String tokenId,
                                        Date controlTime)

Class POEExtraction