With the advancement of digitalization, companies and individuals have come replacing paper with electronic processes increasingly secure. The exchange of documents by digital means has become common in sectors such as legal, financial, real estate and human resources. It is in this scenario that the encrypted digital signature stands out as an essential tool.
This trend comes from the pressing need to adopt reliable methods to ensure that digital files are authentic, tamper-proof and legally valid.
Continue reading to the end to understand how cryptographic signatures ensure the identity of the signer and also protect the signed content from malicious changes.
How Asymmetric Encryption Works
The basis of encrypted digital signatures is asymmetric cryptography, a security method that uses a pair of keys: one public and one private. These keys are mathematically related, but they work in a complementary way.
The private key is known only to the holder and is used to digitally sign a document. The public key is made available to anyone and is used to verify the authenticity of the signature.
This technology prevents third parties from modifying a document without the change being detected. If the signed content is tampered with, the signature verification will fail, alerting the recipient of possible fraud or data corruption.
This process is different from symmetric encryption, which uses the same key to encode and decode information. Asymmetry ensures greater security by allowing the authentication is done without sharing the private key, reducing the risk of compromising the user's digital identity.
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The functions of public and private keys
At the heart of how encrypted digital signatures work are cryptographic keys. The private key is used at the time of signing. When this key is applied to a document, a unique code — called a hash — is created that faithfully represents the signed content. This hash is then encrypted with the private key, generating the digital signature.
The public key comes into play in verification. Anyone can use it to decrypt the signature and check whether the hash matches the contents of the document. If the document has been altered, even by one character, the hash will not match, invalidating the signature.
This mechanism ensures four fundamental pillars for digital security: authenticity, integrity, confidentiality and irrevocability.
Authentication is guaranteed because only the holder of the private key is able to generate the corresponding signature. The integrity of the document is preserved, since any modification to the original content will be promptly identified.
Although the main purpose of the signature is not to encrypt information, the use of keys also makes it possible to protect the content in certain contexts, contributing to confidentiality. Finally, irrevocability prevents the signatory from later denying authorship of the signature, since it is directly linked to his/her private key.
Main algorithms used in encrypted digital signature
Encrypted digital signatures rely on robust mathematical algorithms to maintain their reliability. Below are the best-known ones.
RSA (Rivest-Shamir-Adleman)
One of the first asymmetric encryption algorithms, still widely used for its security and efficiency. It works with long and complex keys, making it difficult to break the protection by brute force.
ECDSA (Elliptic Curve Digital Signature Algorithm)
It uses elliptic curves to create more compact and faster digital signatures while maintaining a high level of security. It is ideal for environments with limited computing resources, such as mobile devices.
Both algorithms are present in digital certificates issued by certification authorities and in solutions that follow the standards of the Brazilian Public Key Infrastructure (ICP-Brasil).
The role of the ICP-Brasil digital certificate
ICP-Brasil is the hierarchical chain responsible for validating digital identities in Brazil. It ensures that a digital signature has the same legal value as a handwritten signature on paper. To this end, it issues digital certificates, which function as an electronic identity for an individual or legal entity.
This certificate is what links the public key to a verified identity. It contains data about the holder, the validity of the Valid identity document, the certification authority and other technical information. By using an ICP-Brasil certificate, the signatory attests, in a legally valid manner, the authorship of an encrypted digital signature.
There are different types of certificates, such as A1, which is stored on the computer, and A3, which requires a physical device, such as a USB token or a chip card. Both can be used to digitally sign legally valid documents, but the choice depends on the user's needs and the desired level of security.
Authenticity, integrity and legal validity guaranteed
The use of encrypted digital signatures provides important technical and legal guarantees for those who need to handle sensitive documents. In the digital environment, simply visually verifying the signature is not enough. It is necessary to have a secure and auditable mechanism that ensures the veracity of the content and the identity of the signatory.
When a person signs a digital contract with their private key and the recipient uses the corresponding public key to verify the signature, the process proves that the document has not been altered since it was signed, that the signatory is really who they say they are; and that the signature is linked to a valid digital certificate and, if issued by a recognized authority, has full legal value.
It is precisely these characteristics that make the technology especially useful in situations such as transactions commercials, labor agreements, legal validations, supplier contracts and other formal contexts.
How to get an encrypted digital signature
To start using an encrypted digital signature, the user must acquire a digital certificate from a certification authority accredited by ICP-Brasil. The issuance process involves the steps below.
- Choosing the certification authority: Companies such as Serasa, Certisign, Valid, among others, offer this service.
- In-person or remote identity verification: to ensure that the certificate will be issued to the correct person.
- Generation and storage of cryptographic keys: The private key is generated on the user's device or token, and must be kept protected.
- Certificate installation and use: After issuance, the certificate can be used on platforms compatible with digital signatures.
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Practical examples of use
Encrypted digital signatures are useful in many everyday business and personal situations. Here are some examples:
Signing of employment contracts
Companies can send contracts to candidates or employees, who sign them remotely with legal validity, eliminating travel and optimizing hiring time. This contributes to more agile and less bureaucratic selection processes.
Legal documents and petitions:
Lawyers and legal professionals use digital certificates to sign electronic petitions on court platforms, ensuring legal validity and respecting the requirements demanded by judicial systems.
Commercial agreements between companies
Suppliers and customers formalize contracts, terms of commitment and other negotiations digitally, securely and quickly. The use of encrypted digital signatures strengthens trust between the parties and reduces the risk of document fraud.
Authorization of bank transactions
Financial transactions with a higher level of sensitivity and value involved can be authenticated digitally, with accurate recording of the actions performed and data protection against unauthorized access. This increases transparency and accountability in the processes.
The use of this technology reduces processing time, eliminates the cost of paper and transportation of physical documents, and reinforces the legal security of any process.
How to sign a document securely
Signing digitally is simple, as long as the platform used follows the correct security standards. The basic process involves the following steps.
- Access to the subscription platform: It could be the company's own system, a legal tool or specific solutions, such as ZapSign.
- Sending the document: the user chooses the file to be signed.
- Subscription type selection: In some cases, it is possible to choose between an electronic signature and a signature with a digital certificate.
- Applying the signature with the private key: The platform performs this step automatically, protecting the user's key.
- Verification and audit: At the end, the document generates a report that shows the signature data, the signatory's identity, date and time, ensuring traceability.
It is worth remembering that some platforms, such as ZapSign, allow integration with emails, internal systems, CRMs or mobile applications, facilitating use in different contexts.
Security and compliance in modern solutions
Digital signature platforms have been modernizing to serve different types of users. One example is ZapSign, which offers solutions with advanced technology, without technical complications.
The tool allows sending, signing and managing documents 100% online, with support for different types of signatures, including those based on a digital certificate.
Companies that adopt this type of solution gain agility, reduce bureaucracy and improve customer experience. All this while maintaining compliance with current legal standards, such as MP 2.200-2/2001, which recognizes the legal validity of digitally signed documents.
Encrypted digital signatures are a powerful ally in the era of digital transformation. They offer security, legal validity and practicality for companies and users who deal with contracts, financial documents, authorizations and other sensitive records.
With asymmetric encryption, the use of secure keys and the support of digital certificates, it is possible to guarantee that the signed document is authentic, complete and legally recognized.
Modern solutions, such as the one offered by ZapSign, make this process more accessible, safe and efficient. For those looking to reduce risks and simplify operations, it is worth knowing the ZapSign platform, which facilitates the use of encrypted digital signatures with full legal compliance.
Getúlio Santos is the CEO of ZapSign, a lawyer, technology enthusiast, and entrepreneur.
