.. _sphx_glr_api_gallery_structures_hash_chains:

Hash chains
-----------

Repeated hashing as a source of one-time secrets.


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


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    <div class="sphx-glr-thumbnails">

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    <div class="sphx-glr-thumbcontainer" tooltip="Lamport proposed logging in without ever sending a reusable password. Hash a secret seed n times and give the server only the last value. Each login reveals the value before it: the server hashes it once and compares. A captured password is useless, because the next one is its preimage. This became S/KEY (1995), and hash chains reappear in blockchains as commit-reveal randomness and in Lamport-style signatures.">

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  .. image:: /api/gallery/structures/hash_chains/images/thumb/sphx_glr_plot_01_lamport_hash_chain_thumb.png
    :alt:

  :doc:`/api/gallery/structures/hash_chains/plot_01_lamport_hash_chain`

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      <div class="sphx-glr-thumbnail-title">Hash chains and one-time passwords (Lamport 1981)</div>
    </div>


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    </div>


.. toctree::
   :hidden:

   /api/gallery/structures/hash_chains/plot_01_lamport_hash_chain