Digital Signature in JavaScript: Enhancing Security and Trust in Digital Documents

Introduction

Digital Signatures play a crucial role in the digital world, serving as the electronic equivalent of a physical signature on paper. However, they offer numerous advantages over traditional ink-and-paper signatures. By creating a unique signing fingerprint, digital signatures can secure and protect digital documents, ensuring the identity of the sender and verifying that the document hasn’t been altered.

Advantages of Digital Signatures

Authentication

A digital signature provides precise identification of the document’s creator or signer. When a signature is valid, the sender’s identity is authenticated.

Integrity

Digital signatures enable easy validation of whether the document’s content has been tampered with after signing. They ensure the integrity of the document.

Non-repudiation

With a digital signature, the signer cannot deny having signed the document. Non-repudiation is a crucial factor in establishing trust.

Apryse SDK Benefits

Apryse SDK offers a range of benefits for digital signatures:

  • Import signature fields via XFDF/FDF format.
  • Export signature data via XFDF/FDF format.
  • Built-in support for PKI signing, including PFX digital certificates.
  • Support for custom signature handlers.
  • Flexibility to sign with images, ink annotations, or create entirely custom appearances.

How Digital Signatures Work

A digital signature generates a unique value (hash/digest) by combining the document data and private key. During verification, the document data and public key are used to generate the same unique value. If the values match, we can confidently say that the data hasn’t been altered and the digital signature is valid.

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ds-diagram

E-Signatures vs Digital Signatures

While an e-signature is an annotation with no additional identifiable information about the creator, a digital signature uses a cryptographic algorithm to uniquely identify the author. Any alterations to the document, including annotations or e-signatures, would result in an invalid digital signature validation.

The Role of Certificate Authorities (CAs)

A cryptographic digital signature can utilize a Certificate Authority (CA) as a trusted third party between the sender and other parties involved.

ca-diagram

A CA issues a digital certificate containing a public key and the owner’s identity. The private key, which matches the public key, is kept secret by the owner. The certificate serves as validation by the CA that the public key belongs to the entity noted in the certificate. The CA’s responsibility is to verify the applicant’s credentials to establish trust and authenticity.

ca-diagram

Public Key Infrastructure (PKI) and Certificate Validation

To ensure the verifiability of a public key owner and the cryptographic signature, a Public Key Infrastructure (PKI) is commonly deployed. A PKI validates the public key owner through a CA. The digital signature and the CA work together to authenticate the owner and the data.

It’s important to note that a CA is required when a third party entity needs to be involved between the sender and other parties. However, if a CA is not used, a digital signature can still utilize a self-signed certificate, as demonstrated in our digital signature sample or web viewer demo.

Expiry and Revocation of Digital Signatures

A document signed using a certificate without additional features such as Document Timestamping (DTS) or Long Term Validation (LTV) will eventually expire, as every certificate has an expiry date when generated.

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In cases where a certificate becomes invalid before reaching its expiration date, a process called Certificate Revocation occurs. The revocation happens for various reasons, as outlined in RFC 5280 Section 5.3.1. Revoked certificates are placed on a Certificate Revocation List (CRL).

This combination of expiration and revocation ensures that digital signatures remain valid for a specific period, based on the certificate’s expiration date and revocation status.

Enhancing Validity with Document Timestamping (DTS) and Long Term Validation (LTV)

To maintain the validity of signatures beyond the certificate’s expiration timeframe or even if the certificates have been revoked, Document Timestamping is applied. A third-party trust provider, such as a Certificate Authority, certifies the secure time (timestamp) of the certificate. Applications validating signatures can then check if the certificate was valid at that time.

For long-term validation of signatures, the application of Long Term Validation (LTV) ensures that even if a CA’s CRL responder becomes inactive, the signatures can still be validated based on their applied time.

It’s worth noting that DTS and LTV are often applied together, although they are separate features.

ProgramMatek’s WebViewer: A Powerhouse for Digital Signatures

ProgramMatek’s JavaScript PDF library, WebViewer, includes a built-in signature tool that allows users to create signature annotations. These annotations are compliant with the PDF specification, acting as freehand or ink annotations. With WebViewer, you can preview, save, and apply default signatures seamlessly.

WebViewer also supports digital signatures, enabling you to digitally sign and certify PDF documents. You can explore the digital signature sample here.

One notable difference between digital signatures and signature annotations is that digital signatures employ asymmetric cryptography, providing an extra layer of security. Signature annotations, on the other hand, are superficial and can move around the document freely.

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Apryse’s Sign App: Empowering Secure Document Signing

Sign App is a powerful application that leverages Apryse, React-Redux, and Firebase to provide a seamless signing experience. Users can request signatures, place signature fields, sign documents, and review signed documents using the Apryse PDF SDK.

To expedite development and reduce time to market, we provide the full source code on our GitHub repo.

The Sign App sample offers the following functionalities:

  • Build a signing application that leverages Apryse, React-Redux, and Firebase.
  • Utilize the built-in signature tool for signature creation.
  • Interact with signature form fields and utilize the signature tool or APIs.
  • Digitally sign PDF documents.
  • Certify PDF documents.

Conclusion

Digital signatures revolutionize document security and trust in the digital era. With their ability to authenticate, ensure integrity, and provide non-repudiation, they offer unparalleled advantages over traditional signatures.

By leveraging Apryse’s powerful SDK and exploring the capabilities of ProgramMatek’s WebViewer, you can unlock the full potential of digital signatures and enhance the security of your digital documents.

ProgramMatek: Empowering Secure Digital Signatures