Beyond Sending: How Hash Technology Ensures the Legal Validity of Registered Emails

In the world of digital communications, a key question often arises:
how can we prove not only that an email was sent, but that its content has not been altered over time?

The answer lies in the technical integrity of the information, guaranteed through a widely accepted cryptographic standard: SHA-256 hash. This technology is one of the pillars that make a registered email from eEvidence a solid legal evidence.

Below, we explain how it works and what is exactly recorded during the certification process.

1. The Unique Digital Fingerprint: What Is a Hash

The core of the technical validity of a registered email lies in the use of hash functions. A hash can be understood as a mathematical digital fingerprint, unique and irreversible, associated with a specific file or content.

The system calculates a hash code for both the complete content of the email (header, body, attachments) and for each attached file individually. This mechanism is based on two fundamental properties:

• Exclusive identity: two different files never generate the same hash. Changing a single comma, a space, or a byte produces a completely different result.
• Integrity proof: if a file maintains the same hash as the one initially recorded, it is mathematically proven that it is exactly the same and that it has not been modified since its certification.

This property is what allows electronic evidence to be verifiable even years later.

2. What Elements Are Recorded in a Certification

For the evidence to be complete, the certification process is not limited to the fact of sending. The entire context of the message is recorded, including:

• Complete content and attachments: the full body of the email and all attached files are certified, without exception.
• Digital fingerprints (SHA-256 hash): the hash of each certified element is calculated and stored.
• Transmission context, which provides technical traceability:
  • For sent emails, the acceptance of the message by the recipient’s server is recorded.
  • For received emails, the provenance of the message is certified, accrediting its origin.

This set of data forms a coherent technical evidence that links content, files, and metadata in a single unalterable record.

Practical tip: through the auto-registration functionality (by sending an email to a dedicated registration address), it is possible to certify only the content and attachments, even without external recipients. This is especially useful for accrediting the existence, integrity, or authorship of sensitive documentation or intellectual property.

3. An Open, Verifiable, and Transparent Standard

Trust in this system is not based on the authority of a provider, but on mathematical verifiability. The SHA-256 algorithm is a public, documented, and widely used standard in areas such as cybersecurity, electronic signature, or blockchain technology.

This provides an essential advantage: anyone can verify the validity of the evidence.

It is enough to use any external SHA-256 calculation tool, process the original file, and verify that the result exactly matches the hash recorded in the certificate. If it matches, integrity is proven without room for interpretation.

Frequently Asked Questions (FAQ)

What Happens If Someone Modifies a Certified File?

Any modification, no matter how minimal, generates a different hash. This makes the alteration immediately detectable and causes the document to lose its correspondence with the original evidence.

Does the Hash Prove That the Recipient Read the Email?

No. The hash proves the integrity of the content, not the reading. Certification accredits sending, content, and technical acceptance at destination, which is what is legally relevant.

Can I Verify the Hash Without Depending on eEvidence?

Yes. The use of SHA-256 allows verifying the evidence with external tools, without the need for proprietary software.

Does This Type of Evidence Have Legal Validity?

Yes. The combination of cryptographic integrity, timestamping, and technical traceability is fully admissible as electronic evidence in legal proceedings.

Conclusion

The legal validity of a registered email does not depend on opinions or interpretations, but on verifiable mathematics.

Thanks to the use of hash functions such as SHA-256, the content, attachments, and transmission data are linked in an unalterable way, creating robust and lasting technical evidence. This approach makes registered email a reliable tool for protecting rights, accrediting facts, and providing legal security in any digital context.