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Certified by

This document is a zip file named full_zip_file that weighs 0.15 MB and whose contents you can extract and inspect next.

Full document: full_zip_file
Part 1: 1_full_stack_developer.html
Certification date on Bitcoin's blockchain: {loading date}.
Digitally signed by: Integrations Team Constata , Responsable de la Organización at Constata EU Digital Trust Services S.L.. Email address teams@constata.eu. Constata User #304.
Signed on: {loading date }
Signature: H5OTOCuD3i+qFmAvfyQelT53u8cDAbbH2wrl68Joz96mTb0sz9pGfBpmg7BOHbOAYwJkxIKKwqfOcbN0ln7BJDg=
Public key: 1EPVW9bhCmvY3TVTn7GtfEXW8Y23biZC1b

This is a timestamp certificate with legal and technical validity, it's backed by the existence of specific data that can only be generated from the contained documents, and that was written with certain date in a public, immutable, distributed database known as Bitcoin's blockchain.

The certificate is this very file that you've downloaded or received. You can re send it to third parties by any means available to you, and the may validate it independently.

⛓️ Independent verification in Bitcoin Blockchain

In case Constata's web validation is not available, or the company's endorsement was not enough, you can access a detailed audit of this certificate clicking here.

Certificate Audit

We describe the process and technologies involved in the issuance and validation of this certificate Terminology is available in the Glossary at the bottom.

To leave evidence that the documents contained in this certificate existed before a certain date CONSTATA produced files, called BULLETINS, that contain the HASHES of each PART of a DOCUMENT contained in this CERTIFICATE, and the HASHES of the DIGITAL SIGNATURES applied to some of thos PARTS.

Then, we left proof of the HASH> of each BULLETIN in separate BITCOIN TRANSACTIONS that were written in the BITCOIN BLOCKCHAIN distributed database on a date referred to as BLOCK DATE

We can establish then that DOCUMENTS, and DIGITAL SIGNATURES applied to them, existed at the time BLOCK DATE of the BULLETIN associated with them.

You can validate that the DIGITAL SIGNATURES applied to DOCUMENTS are correct independently, but the link between those signatures and actual persons and companies is only endorsed by CONSTATA's signature that was applied to this file as a whole.

Unlike timestamps, validating signatures requires you acquire a copy of constata's public key from a trusted source. Constata's website is one such way. If you are unsure about Constata's public key, then you cannot be sure about who signed this document, and who's endorsing the signer identities.

Javascript validation

This file contains the timestamp and digital signature validation routines implemented in the Javascript language, you can find it in this file's source code. When you opened your web browser, this routine was executed, and several public copies of the Bitcoin blockchain were queried in search for bulletin fingerprints.

The process was successful, otherwise, this certificate would have shown an error message.

Manual timestamp validation, step by step

If you're not familiar with Javascript, or if you rather perform the validation manually, this are the steps to follow. This steps are to be reproduced in a command prompt on any Linux, MacOS or compatible operative system.

Validate Bulletins

With this process, we validate that the BULLETINS were published on the BITCOIN BLOCKCHAIN at the matching date. This way we can know that the DOCUMENTS referred to existed at that date.

Validate BULLETIN #3083

  1. Save BULLETIN #3083 locally.

  2. Calculate its HASH. 

                    $ shasum -a 256 /path/to/bulletin_3083.txt
                23db98f5f26c05a81ad55400a2426ff39038e1025034b23fbbaa511dd00e08f0

  3. Query the BITCOIN TRANSACTION to find the BULLETIN HASH. Its transaction id is 9c4e0d070124548a46fe2382af3aff6029bcabf23799aa3feb58d5bc534e34d7.

    At Blockchain.com

    1. Visit the transaction page.
    2. Check the "Pkscript" setion to validate it contains the HASH: 23db98f5f26c05a81ad55400a2426ff39038e1025034b23fbbaa511dd00e08f0
    3. Check the field Timestamp shows the date 24-April-2023 21:13HS. (beware of timezones).

    At Mempool.space

    1. Visit the transaction page.
    2. Expand the "Details" section.
    3. Validate it contains the HASH: 23db98f5f26c05a81ad55400a2426ff39038e1025034b23fbbaa511dd00e08f0
    4. Review the field Timestamp shows the date 24-April-2023 21:13HS.

    At Blockstream.com

    1. Visit the transaction page
    2. Expand the "Details" section.
    3. Validate it contains the HASH: 23db98f5f26c05a81ad55400a2426ff39038e1025034b23fbbaa511dd00e08f0
    4. See the Timestamp shows the date 24-April-2023 21:13HS.


DOCUMENT validation

With this process we validate all the DOCUMENTS are being referenced by one of the included BULLETINS we just validated, and therefore, existed in the date specified by the matching BULLETIN.

Validate DOCUMENT #1

This document is composed of 2 parts, was included in BULLETIN #3083, with date {loading date}

  1. Save the part "full_zip_file" locally.

  2. Calculate its HASH. 

                        $ shasum -a 256 /path/to/1_full_zip_file
                    f2f92c9b25d80b22ba5e5e08dd045e58844fa997cd0d259648e48b5b28f76dd2

  3. Find this part's HASH in BULLETIN 3083 you saved previously, if the 'grep' command returns '1' it means the HASH is present there. 

                        $ grep --count f2f92c9b25d80b22ba5e5e08dd045e58844fa997cd0d259648e48b5b28f76dd2 /path/to/boletin_3083.txt
                    1
  1. Save the part "1_full_stack_developer.html" locally.

  2. Calculate its HASH. 

                        $ shasum -a 256 /path/to/1_1_full_stack_developer.html
                    ae17d37ec87f6df97e4995b66960e0ab8706cfa433c1b68c7a2834d0ffcc4e77

  3. Find this part's HASH in BULLETIN 3083 you saved previously, if the 'grep' command returns '1' it means the HASH is present there. 

                        $ grep --count ae17d37ec87f6df97e4995b66960e0ab8706cfa433c1b68c7a2834d0ffcc4e77 /path/to/boletin_3083.txt
                    1


Glossary

Bitcoin Blockchain
Public database, wrote incrementally as a sequence of immutable blocks using a proof of work algorithm, globally distributed and freely accesible.

Block Date
Date in wich a TRANSACTION was written to the BITCOIN BLOCKCHAIN.

Block Explorer
A website managed by an independent centralized third parte that provides information about the date in which a TRANSACTION was written immutably in the BITCOIN BLOCKCHAIN. There are múltiple publicly accesible block explorers, and it's possible for anyone to install their own, so they don't need to trust the website managers.

Bulletin
Instrument composed of DOCUMENT digital hashes (fingerprints) associated to it. The BULLETIN's HASH is written into the BITCOIN BLOCKCHAIN producing a TIMESTAMP for all the DOCUMENTS contained in the BULLETIN. The BULLETIN contents are included in the TIMESTAMP CERTIFICATE. The BULLETIN data and the DOCUMENTS are never included in the BITCOIN BLOCKCHAIN.

Certificate
Digital attestation that contains the certified DOCUMENTS, the BULLETIN, the blockchain TRANSACTION ID where the BULLETIN's HASH was written, and the algorithm that can be used to validate it. This certificate can be validated by third parties receiving it, without CONSTATA's intervention.

Constata
Company founded by experienced technologists and lawyers, to provide digital trust services, focusing in TIMESTAMP and digital signature certifications using, unlike most providers, a public, immutable, and distrubited record database which is the BITCOIN BLOCKCHAIN, and the DIGITAL SIGNATURE technology used by Bitcoin wallets.

Document
Electronic file or message sent by a USER to CONSTATA to have a TIMESTAMP applied to it. It contains one or more PARTS that are individually TIMESTAMPED and may be DIGITALLY SIGNED. The DOCUMENT is stored by CONSTATA for 5 years in its own servers, along with its TIMESTAMP CERTIFICATE.

Hash (also, digital fingerprint)
The result of applying a cryptographic algorithm to a dataset, that is unique, univocal for each dataset, unidirectional, and thus it does not retain any information about the original dataset, and can only be calculated again using said dataset.

Part
Section of a DOCUMENT that can be interpreted and extracted as an independent file. It receives a TIMESTAMP and may receive DIGITAL SIGNATUREs made by CONSTATA's USERs.

Signature, Digital
Instrument generated with information privately held by a signer, that allows to establish their consent or approval about the contents of a DOCUMENT. A series of mathematical operations make this signature unique, authentic and can be verified by the person receiving the signed DOCUMENT.

Timestamp
Data in electronic format that references other data, and links it to a specific date, giving proof that the data is at least as old as that specific date.

Transaction, Bitcoin
Fundamental registry made by a USER and propagated to the Bitcoin network to be written in the BITCOIN BLOCKCHAIN. In Constata's case, all TRANSACTIONS produced have the sole purpose of writing a BULETTIN's HASH in the BITCOIN BLOCKCHAIN.