707b5842cb
In the related community PR we move from hash on send (back) to hash on post See community PR. This commit adapts related documentation. task-4095970 Part-of: odoo/documentation#10906 Related: odoo/odoo#178915 Related: odoo/enterprise#69324 Related: odoo/upgrade#6458 Signed-off-by: Sven Führ (svfu) <svfu@odoo.com>
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================================
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Data inalterability check report
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================================
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Tax authorities in some countries require companies to **prove their posted accounting entries are
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inalterable**, meaning that once an entry has been posted, it can no longer be changed.
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To do so, Odoo can use the **SHA-256 algorithm** to create a unique fingerprint for each posted
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entry. This fingerprint is called a hash. The hash is generated by taking an entry's essential data
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(the values of the `name`, `date`, `journal_id`, `company_id`, `debit`, `credit`, `account_id`, and
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`partner_id` fields), concatenating it, and inputting it to the SHA-256 hash function, which then
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outputs a fixed size (256-bit) string of characters. The hash function is deterministic (:dfn:`the
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same input always creates the same output`): any minor modification to the original data would
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completely change the resulting hash. Consequently, the SHA-256 algorithm is often used, among
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others, for data integrity verification purposes.
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In addition, the previous entry's hash is always added to the next entry to form a **hash chain**.
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This is used to ensure a new entry is not added afterward between two posted entries, as doing so
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would break the hash chain.
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.. note::
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Hashes generated by the SHA-256 algorithm are theoretically not unique, as there is a finite
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number of possible values. However, this number is exceptionally high: 2²⁵⁶, which is a lot
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bigger than the number of atoms in the known universe. This is why hashes are considered unique
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in practice.
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.. _data-inalterability/lock:
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Lock posted entries with hash
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=============================
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To start using the hashing function, go to :menuselection:`Accounting --> Configuration > Journals`.
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Open the journal for which you want to activate the feature, go to the :guilabel:`Advanced Settings`
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tab, and enable :guilabel:`Lock Posted Invoices with Hash`.
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This feature is available for sale, purchase, and general journals.
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To compute the hash of an entry, Odoo retrieves the predecessor entries of the chain (i.e., the
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entries with the same sequence prefix) and hashes them in a continuous way from the last hashed
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entry to the new entry to hash.
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.. warning::
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Once you post an entry in a locked journal, you cannot disable the feature anymore, nor edit any
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locked entry.
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.. _data-inalterability/report:
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Report download
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===============
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To download the data inalterability check report, go to :menuselection:`Accounting --> Configuration
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--> Settings --> Reporting` and click on :guilabel:`Download the Data Inalterability Check Report`.
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The report's first section is an overview of all your journals and their configuration. Under the
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inalterability check column, you can see whether or not a journal's entries are locked with a hash
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(V) or not (X). The coverage column tells you when a journal's entries started being locked.
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.. image:: data_inalterability/journal-overview.png
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:align: center
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:alt: Configuration report for two journals
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The second section gives you the result of the data consistency check for each hashed journal. You
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can view the first hashed entry and its corresponding hash and the last hashed entry and its
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corresponding hash.
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.. image:: data_inalterability/data-consistency-check.png
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:align: center
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:alt: Data consistency check report for a journal
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