Handling of verification chains in the authentication of data streams
Apparatuses and methods for checking a data stream on trustworthiness are described. According to an aspect, the data stream indicates, whether a segment is a first segment or whether a segment is a last segment of assigned sequence of segments. According to another aspect, an apparatus for decoding a data stream is configured for deriving, from the data stream, whether a verification chain within a temporal sequence of segments is interrupted at a segment.
1 . An apparatus for decoding an audio data stream having an audio signal encoded thereinto, the audio data stream comprising a temporal sequence of segments, wherein the apparatus comprises a processor coupled to the memory is configured, for a segment of the sequence of segments,
determining a predetermined portion of the segment;
deriving, from the audio data stream, an indication which indicates
whether the segment is the first segment of a signed subsequence of the temporal sequence, or
whether the segment is the last segment of a signed subsequence of the temporal sequence;
and deriving, from the audio data stream, a digital signature, which is for being checked against a verification string acquired based on the predetermined portion and based on the indication, deriving, from the audio data stream, the indication, which indicates whether the segment is the first segment of the signed subsequence of the temporal sequence, wherein the apparatus is configured for if the segment is the first segment of the signed subsequence, forming the verification string independent of any portion of the audio data stream, which portion precedes the segment in the temporal sequence;
and if the segment is not the first segment of the signed subsequence, deriving the verification string further based on a previous hash value acquired for the preceding segment of the segment.
2 . Apparatus according to claim 1 , wherein the apparatus is configured for verifying the predetermined portion by checking whether the verification string fits to the digital signature.
3 . Apparatus according to claim 1 , wherein the apparatus is configured for providing the predetermined portion, the indication and the digital signature for a verification of the predetermined portion.
4 . Apparatus according to claim 1 , wherein the predetermined portion is to be subjected to a hash function to acquire a hash value, and wherein the verification string is acquired based on the hash value.
5 . Apparatus according to claim 1 , wherein the predetermined portion and the indication are to be subjected to a hash function to acquire a hash value, and wherein the verification string is acquired based on the hash value.
6 . Apparatus according claim 1 , wherein the checking whether the verification string fits to the digital signature comprises:
decrypting the digital signature to acquire a check value; and
checking whether the verification string matches the check value.
7 . Apparatus according to claim 1 , configured for deriving the indication from a supplemental information message associated with the segment.
8 . Apparatus according to claim 7 , wherein the supplemental information message is indicative of the hash function and/or a certificate for decrypting the digital signature.
9 . Apparatus according to claim 1 , configured for deriving the indication from a supplemental information message, which is indicative of the digital signature.
10 . An apparatus for encoding an audio data stream having an audio signal encoded thereinto, wherein the apparatus comprises a processor coupled to the memory is configured for rendering the audio data stream checkable on trustworthiness, and encoding, into the audio data stream, a temporal sequence of segments, wherein the apparatus is configured for rendering a segment of the sequence of segments checkable on trustworthiness by subjecting a predetermined portion of the segment to a hash function to acquire a hash value;
inserting, into the audio data stream, an indication which indicates
whether the segment is the first segment of a signed subsequence of the temporal sequence, or
whether the segment is the last segment of a signed subsequence of the temporal sequence;
forming a verification string based on the hash value and based on the indication;
acquiring a digital signature based on the verification string,
inserting, into the audio data stream, the indication, which indicates whether the segment is the first segment of the signed subsequence of the temporal sequence, wherein the apparatus is configured for if the segment is the first segment of the signed subsequence, forming the verification string independent of any portion of the audio data stream, which portion precedes the segment in the temporal sequence;
and if the segment is not the first segment of the signed subsequence, deriving the verification string further based on a previous hash value acquired for the preceding segment of the segment.
11 . Apparatus according to claim 10 , configured for, in acquiring the digital signature, signing the verification string.
12 . Apparatus according to claim 10 , configured for inserting the indication into a supplemental information message associated with the segment.
13 . Apparatus according to claim 12 , wherein the supplemental information message is indicative of the hash function and/or a certificate for decrypting the digital signature.
14 . Apparatus according to claim 10 , configured for inserting the indication and the digital signature into a supplemental information message.
15 . A method for decoding an audio data stream having an audio signal encoded thereinto, the audio data stream comprising a temporal sequence of segments, wherein the method comprises, for a segment of the sequence of segments, determining a predetermined portion of the segment;
deriving, from the audio data stream, an indication which indicates
whether the segment is the first segment of a signed subsequence of the temporal sequence, or
whether the segment is the last segment of a signed subsequence of the temporal sequence; and
deriving, from the audio data stream, a digital signature, which is for being checked against a verification string acquired based on the predetermined portion and based on the indication, deriving, from the audio data stream, the indication, which indicates whether the segment is the first segment of the signed subsequence of the temporal sequence, wherein the apparatus is configured for if the segment is the first segment of the signed subsequence, forming the verification string independent of any portion of the audio data stream, which portion precedes the segment in the temporal sequence;
and if the segment is not the first segment of the signed subsequence, deriving the verification string further based on a previous hash value acquired for the preceding segment of the segment.
16 . An audio data stream having an audio signal encoded thereinto, the audio data stream being checkable on trustworthiness, the audio data stream comprising:
a temporal sequence of segments,
an indication which indicates
whether the segment is the first segment of a signed subsequence of the temporal sequence, or
whether the segment is the last segment of a signed subsequence of the temporal sequence,
forming a verification string based on the hash value and based on the indication;
acquiring a digital signature based on the verification string,
inserting, into the audio data stream, the indication, which indicates whether the segment is the first segment of the signed subsequence of the temporal sequence, if the segment is the first segment of the signed subsequence, forming the verification string independent of any portion of the audio data stream, which portion precedes the segment in the temporal sequence;
and if the segment is not the first segment of the signed subsequence, deriving the verification string further based on a previous hash value acquired for the preceding segment of the segment.