Editable signed video data

A method of validating a signed video bitstream obtained by prediction coding of a video sequence,

• the signed video bitstream including data units, associated signature units and an archive object, wherein each data unit represents at most one macroblock in a frame of the prediction-coded video sequence, wherein each signature unit includes a digital signature of a bitstring, and wherein the archive object includes at least one archived fingerprint of a data unit,
• the method comprising:
• obtaining a fingerprint of each data unit associated with a signature unit by
• computing a fingerprint of the data unit, or
• retrieving an archived fingerprint from the archive object;
• deriving a bitstring from the obtained fingerprints;
• and
• validating the data units associated with the signature unit using the digital signature in the signature unit, including:
• verifying the derived bitstring using the digital signature, or,
• if the signature unit includes a bitstring, verifying the bitstring in the signature unit using the digital signature, and comparing the derived bitstring and the verified bitstring.

A non-transitory computer readable recording medium comprising a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method of editing a signed video bitstream obtained by prediction coding of a video sequence, the signed video bitstream including data units and associated signature units, wherein each data unit represents at most one macroblock in a video frame of the prediction-coded video sequence, and wherein each signature unit includes a digital signature of a bitstring derived from a plurality of fingerprints of exactly one associated data unit each, the method comprising:

• receiving a request to substitute a region of at least one video frame;
• determining a first set of macroblocks, in which said region is contained, and a second set of macroblocks referring directly or indirectly to macroblocks in the first set;
• adding an archive object to the signed video bitstream, the archive object including fingerprints of a first and a second set of data units, which respectively represent the determined first and second set of macroblocks;
• editing the first set of data units in accordance with the request to substitute the region of the at least one video frame;
• and
• re-encoding the second set of data units.