These days, we are witnessing a growing scenario of digital activities, from sending important documents to critical financial transactions. Consequently, increasing care is required regarding the safety of these operations. This is where the hash function comes into play. digital signature.
In a simplified way, the hash function can be seen as something similar to a “fingerprint” of a digital file. The hash is unique and can be generated from any type of data, be it a document, an image or even a financial transaction.
Understanding this concept is fundamental for any and all entrepreneurs – even for those without specific training or knowledge in programming.
In this article, we will explain in an accessible and direct way what exactly this hash function is used for in digital signatures. We will see how it plays a decisive role in ensuring the integrity and authenticity of digital documents, providing an extra layer of security for entrepreneurs looking to protect their data and online operations and to strengthen digital security in their business.
What, after all, is the hash function?
The hash function is a powerful digital verification method. This advanced function has the unique ability to transform any type of data into a completely unique sequence of characters.
In other words, we can imagine the hash function as a kind of virtual stamp, or even a “fingerprint” of your electronically signed document. Just as each person has a unique fingerprint, each digital file has its own hash, which uniquely identifies it.
They process is carried out using a special mathematical algorithm. You can think of this algorithm as a secret kitchen recipe, which takes ingredients (your data) and mixes them in a specific way to produce a unique end result, the hash. And the amazing thing is that even if you change just one small detail in your data, the resulting hash will be completely different.
So, when we need to check whether a digital document is the same as the one that was originally sent, we can simply generate a new hash and compare it to the original hash. If they are identical, we know that the document has not been altered – in practice, it is as if we were comparing two fingerprints to see if they belong to the same person.
Thus, the hash acts as a kind of guardian of the integrity of your data, providing a reliable way to verify that everything is as it should be in the digital world. It is, therefore, an extremely powerful security tool – even though we can't see its gears in action, we can trust that it is there, keeping our files safe and intact.
How creating the hash code works
When a document is digitally signed, the hashing process plays an extremely valuable role in verifying its integrity, preventing fraud or alteration. Below is a detailed step-by-step guide so that we can understand how this works, in practical terms.
1. Hash generation
The first step is to generate the hash of the original document. This is done using a special mathematical algorithm that transforms the entire document content into a unique string of characters. This sequence is the hash code.
2. Digital signature
Then, the generated hash code is combined with the sender's (or subscriber's) private key and goes through another mathematical process known as public-key cryptography. This results in a unique digital signature.
3. Attaching the signature to the document
The digital signature, along with the original document, is then attached to the digital document. When going through this process, the document acquires an additional layer of protection, guaranteeing its authenticity and integrity over time.
4. Integrity check
When someone receives the digitally signed document, the verification process begins. First, the receiver extracts the digital signature from the document.
5. Hash extraction
Then the receiver uses the sender's (or subscriber's) public key to decrypt the digital signature and obtain the original hash code.
6. Generation of the new hash
After receiving the digitally signed document, the receiver applies the same mathematical algorithm used to create the original hash to generate a new hash code from the received document.
7. Comparison of hashes
Finally, the receiver compares the original hash code (obtained from the digital signature) with the new hash code generated from the received document. If the hashes match, it means the document has not been changed since it was signed. If they do not match, it indicates that the document has been tampered with in some way.
This process guarantees the integrity of the document, as any modification made to the document after digital signature would result in a new hash code, which would not match the original.
Therefore, digital signature using a hash code provides security, authenticity and integrity to digital documents, making them immune to fraud or unauthorized changes.
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The role of the hash function in the digital signature and its legal validity
The use of the hash function is extremely important in the legal validity of a digitally signed document, ensuring that vital legal requirements are fully met.
This process is especially relevant with regard to the following aspects, which are fundamental pillars for the reliability and legal acceptance of the document.
Authenticity
The authenticity of a signed digital document is essential to ensure that it actually originated from the alleged sender. The hash function acts as a unique “fingerprint” of the document, providing a reliable way to verify its origin.
By comparing the original hash of the document with the hash generated from the received document, it is possible to confirm that the content has remained unchanged since signing. This ensures that the document has not been forged or tampered with, strengthening its authenticity.
non-repudiation
Non-repudiation refers to the inability of a party to deny the authenticity of their signature on a document. With the digital signature and the use of the hash function, it becomes difficult for the sender to deny having signed the document.
Since the digital signature is generated by combining the hash of the document with the sender's private key, only the holder of the corresponding private key can produce a valid digital signature. This prevents the sender from denying their authorship, guaranteeing the non-repudiation of the digitally signed document.
Integrity
The integrity of a digital document is vital to ensure that its contents remain intact and are not altered in unauthorized ways. Using the hash function is absolutely necessary to verify the integrity of the document, as any modification made to the content would result in a different hash.
By comparing the original hash with the hash generated from the received document, it is possible to detect any changes, ensuring that the document remains intact since signing.
Therefore, when it comes to the legality of digitally signed documents, the use of the hash function plays an essential role, helping to guarantee their authenticity, non-repudiation and integrity.
These legal requirements are fundamental to establishing the reliability and legal validity of documents in digital environments, offering security and protection against fraud and legal disputes and providing solidity to the document management.
How to find the hash in documents with a digital signature
Locating the hash code in digitally signed documents is a simple and transparent procedure, which aims to offer convenience to the end user. When receiving a digitally signed document, it is common to have the ability to access the file's properties or details through the document viewing method used. Within these options, you can find detailed information about the digital signature, including the hash code itself.
On various platforms and software, such as PDF readers or electronic signature, just right-click on the document and select the “Properties” or “Details” option. In this section, information regarding the digital signature will be available, including the original hash of the document.
The hash function offers a transparent and accessible process designed to allow users to easily verify the integrity and authenticity of the documents they receive.
It is therefore not necessary to have advanced technical knowledge to carry out this check, making it accessible to all users, regardless of their level of technical skill.
If you want to know more about how electronic signatures are implemented in business management and how this can benefit your organization, we invite you to contact a ZapSign sales representative.
Our experts will be happy to provide detailed information about our e-signature solutions and how they can meet your specific business needs.
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