ZT Browser is developed based on Google's open-source Chromium. It has built-in excellent PDF reading function, seamlessly and quickly loads and views PDF documents when browsing the web, and does not need to install PDF reader software or any other plug-ins. However, ZoTrus Technology does not stop there. It is not satisfied with only providing PDF reading functions, it benchmarks against Adobe Reader and provides multiple innovative functions such as PDF reading, signature verification, document signing, document encrypting and time stamping. It is all-in-one full-featured PDF reader.
1. Verify the digital signature of the document in real time to show the trusted identity of the document
When ZT Browser opens a PDF document, it will check whether the PDF file has a digital signature in real time. If so, it will verify whether it is a trusted digital signature. If it is trusted, it will display the trusted identity information of the signer in real time. Both Certifying Signature and Approval Signature are supported, and the trusted identity information of the signer is displayed in the PDF bar in the same way.
ZT Browser displays various document security-related icons as shown in the figure below. ZT Browser displays the digital signature information of the PDF document in the PDF bar where the PDF file name was originally displayed, and add a "Signature Panel" button 
in front of the Download and Print button on the right, it allows user to view all relevant information of document digital signatures, including trusted signing time, document signing certificate details, LTV detail, timestamp detail, signature algorithm, HASH algorithm, PAdES level, etc. As shown in the figure below, the icons displayed on the left mainly have 6 types of information:
- The first icon is used to show that this document has a digital signature trusted by ZT Browser.
- The second icon is used to show that this document is encrypted.
- The third icon is used to show that this document has timestamped trusted by ZT Browser, which proves that the document signature time is a trusted time.
- The fourth icon is used to show that this document is digitally signed using the SM2 algorithm, which meets the requirements of cryptography compliance for China government documents.
- The fifth icon is used to display the trusted level of the signer’s identity, which is divided into four levels: T1/T2/T3/T4.
- The sixth icon is used to display the country of the document signer, and the following information is the identity information of the signer.
The 5th and 6th icons show the effect according to 4 different trusted levels as shown in the figure below. The T1 trusted level indicates that the document signer only validated the email address, so only the email address is displayed, as shown in Figure 1 below. The T2 trusted level indicates that the document signer has passed the personal identity validation, so the name and country of the signer are displayed, as shown in Figure 2 below. The T3 trusted level indicates that the document signer has passed the organization validation, so the organization name and country are displayed, as shown in Figure 3 below. The T4 trusted level indicates that the document signer is an employee of this organization, not only the personal identity of the employee has been validated, but also the identity of this organization which the employee belongs is validated. Therefore, the employee's name, organization name and country are displayed, as shown in Figure 4 below.
Figure 1
Figure 2
Figure 3
Figure 4The purpose of these icons and information added by ZT Browser is to help users quickly identify the true identity of PDF documents, and not to easily believe the personal identity or organizational identity claimed in the document. This can help users to be able to make correct decision based on these icons when reading documents. so as to avoid being harmed by a fake identity document and protect the user's surfing safety on the Internet.
For PDF documents that have digital signatures, but ZT Browser cannot verify whether they are trustworthy, ZT Browser will display "At least one signature has problem!" in the PDF bar. If the digital signature has been tampered with, it displays "At least one signature is invalid!" For PDF documents without digital signatures, ZT Browser will display "No digital signature, identity is unknown. Be careful!" to prevent being harmed by fake identity documents, because if the document does not have a digital signature, then cannot prove that it is trustworthy, it cannot be considered an authentic and trustworthy document if the document just has a picture of the seal of a government agency, even the PDF file is downloaded from trusted government website since it is not trustworthy without digital signatures because there is no guarantee that this document is not be illegally tampered with or replaced. It is very easy to add a fake official seal image to a document, and digital signatures use cryptographic technology that cannot be counterfeited, which can effectively prevent identity counterfeiting in PDF documents.
2. Verify the authenticity of e-invoices in real time and display the trusted identity of the e-invoice issuer
Since e-invoices have been basically popularized in China, although e-invoices use digital signature technology to prevent counterfeiting and tampering, but the RSA algorithm digital certificate used to digitally sign e-invoice PDF files is not trusted by Adobe Reader, or the PDF signing certificate used SM2 algorithm that cannot be recognized by Adobe Reader. Therefore, when you use Adobe Reader to open the e-invoice, it will display "At least one signature has problem" or "At least one signature is invalid", this will not play the anti-counterfeiting role of digital signatures and will also make users at a loss.
There are two solutions to solve this problem. One is to apply Adobe trust for the root CA certificate of the document signing certificate for signing e-invoice. However, this is not only difficult, but the future trend is to popularize the use of SM2 algorithm document signing certificate, applying for trusted root CA cannot solve this problem. The second solution is that document Reader trust these e-invoice signing certificates and support the SM2 algorithm to verify e-invoice digital signature. ZoTrus Technology adopts the second solution.
ZT Browser PDF Reader trust commonly used e-invoice signing certificates, it can not only verify whether the digital signature of the e-invoice is trusted in real time and verify whether the e-invoice has been tampered with, but also directly display the authenticity of the e-invoice in PDF bar, allowing users to know the authenticity of the e-invoice when reading it. Users can click the "Signature Panel" icon to view the identity information of the issuer of this e-invoice, that is, the identity information of the signing certificate, to further understand the e-invoice details. For e-invoices whose invoice amounts have been maliciously tampered with, it will definitely fail to pass the digital signature verification. ZT Browser will display warning that this is a fake e-invoice - "Fake e-invoice, Not pass the verification!" There is no need to go to the official e-tax website for verification, read it and complete the verification immediately. This is the power of digital signature. For e-invoices without trusted digital signatures, ZT Browser will display "No digital signature" or "At least one signature has problem " just like other PDF documents.
3. ZT Browser will provide more document security services
In addition to providing excellent PDF document reading services, automatic verification of the digital signatures in PDF file, display the trusted identity of the signer, ZT Browser will also provide document digital signing and timestamping services, as well as document encryption services. These services will be available for free or for a fee in different service types, so stay tuned.
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