question: protected void addReferencesFromOfflineCRLSource ( List < TimestampReference > references ) { OfflineCRLSource crlSource = getCRLSource ( ) ; if ( crlSource != null ) { List < X509CRL > containedX509CRLs = crlSource . getContainedX509CRLs ( ) ; if ( CollectionUtils . isNotEmpty ( containedX509CRLs ) ) { usedCertificatesDigestAlgorithms . add ( DigestAlgorithm . SHA1 ) ; for ( X509CRL x509crl : containedX509CRLs ) { final byte [ ] digest = DSSUtils . digest ( DigestAlgorithm . SHA1 , DSSUtils . getEncoded ( x509crl ) ) ; references . add ( new TimestampReference ( DigestAlgorithm . SHA1 , Base64 . encodeBase64String ( digest ) , TimestampReferenceCategory . REVOCATION ) ) ; } } } }
target:  This method adds references to retrieved CRL responses from LT level. With LTA level, we have a proof of existence