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To address non-repudiation concerns an association must be made between the electronic document and some distinctive item of data that identifies the signing party, in a way that makes the signature attributable to the signing party. To address integrity concerns the document and the association to the signing party must be stored and retrieved in such a way that any alteration in either would be detected; i.e., the storage and retrieval must be "tamper evident".
There are
Generally the alternatives that are least expensive, easiest to implement, and most convenient for the