add a given extension field for the standard extensions tag
The value parameter becomes the contents of the octet string associated
with the extension.
Returns an appropriately initialised digest calculator based on the message imprint algorithm
described in the first time stamp in the TemporalData for this message.
Returns an appropriately initialised digest calculator based on the message imprint algorithm
described in the first time stamp in the TemporalData for this message.
Validate the timestamp request, checking the digest to see if it is of an
accepted type and whether it is of the correct length for the algorithm specified.