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Linked timestamping is a type of trusted timestamping where issued time-stamps are related to each other. ==Description== Linked timestamping creates time-stamp tokens which are dependent on each other, entangled into some authenticated data structure. Later modification of issued time-stamps would invalidate this structure. Temporal order of issued time-stamps is also protected by this data structure, making backdating of the issued time-stamps impossible, even by the issuing server itself. Top of the authenticated data structure is generally ''published'' in some hard-to-modify and widely witnessed media like printed newspaper. There are no (long-term) private keys in use, avoiding PKI-related risks. Suitable candidates for authenticated data structure are: * Linear hash chain, * Merkle tree (binary hash tree), * Skip list. Simplest linear hash chain based time-stamping is illustrated on following drawing: The linking-based time-stamping authority (TSA) usually performs the following distinct functions: ;Aggregation :For increased scalability TSA might group time-stamping requests arriving within a short timeframe. These requests will be ''aggregated'' together without retaining their temporal order and then assigned the same time value. Aggregation creates cryptographic connection between all involved requests; authenticating aggregate value will be used as input for the ''linking'' operation. ;Linking :Linking creates verifiable and ordered cryptographic link between current and already issued time-stamp tokens. ;Publishing :TSA ''publishes'' periodically some links, so that all previously issued time-stamp tokens depend on the published link and that it is practically impossible to forge the published values. By publishing widely witnessed links the TSA creates unforgeable verification points for validating all previously issued time-stamps. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Linked timestamping」の詳細全文を読む スポンサード リンク
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