.. _sphx_glr_api_gallery_structures_timestamps:

Timestamping
------------

Proving that a document existed by a given time.


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  <div id='sg-tag-list' class='sphx-glr-tag-list'></div>


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    <div class="sphx-glr-thumbcontainer" tooltip="Haber and Stornetta asked how to timestamp a digital document so that not even the timestamping service could backdate it. Their answer: each certificate includes the hash of the previous one. Changing any old record changes its hash, which breaks every later link. A blockchain is this chain of linked timestamps, with blocks as the records.">

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  .. image:: /api/gallery/structures/timestamps/images/thumb/sphx_glr_plot_01_linked_timestamps_thumb.png
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  :doc:`/api/gallery/structures/timestamps/plot_01_linked_timestamps`

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      <div class="sphx-glr-thumbnail-title">Linked timestamps: tamper evidence by hashing the past (Haber and Stornetta 1991)</div>
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    <div class="sphx-glr-thumbcontainer" tooltip="Linking every document into a chain costs one record per document. Bayer, Haber and Stornetta batched them: put a round&#x27;s documents in a Merkle tree and timestamp only the root. Each document keeps a short proof linking it to that root. This is exactly how a block commits to its transactions.">

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  .. image:: /api/gallery/structures/timestamps/images/thumb/sphx_glr_plot_02_merkle_batching_thumb.png
    :alt:

  :doc:`/api/gallery/structures/timestamps/plot_02_merkle_batching`

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      <div class="sphx-glr-thumbnail-title">Batching timestamps with a Merkle tree (Bayer, Haber and Stornetta 1993)</div>
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    </div>


.. toctree::
   :hidden:

   /api/gallery/structures/timestamps/plot_01_linked_timestamps
   /api/gallery/structures/timestamps/plot_02_merkle_batching