Addendum to Digital signatures for PDF documents
The Digital Signatures for PDF documents eBook has been one of our most popular downloads since it was written. Although many of the principles and concepts remain the same, iText itself has changed a great deal over the years.
The code snippets included in the eBook were accompanied by complete examples which we made available on our website. As these examples were originally written for iText 5, they have been completely updated and rewritten for the latest versions of iText 7. This meant significant changes in some cases, and some examples were no longer applicable to iText 7.
This addendum links to pages with updated Java and .NET (C#) examples for each chapter of the eBook, and the table below notes the name of the example and which chapter the code example corresponds to:
| Example Name | Description and Notes |
|---|---|
| Chapter 1 | Understanding the concept of digital signatures |
| DigestDefault | An example showing how to use the MessageDigest class |
| DigestBC | An example demonstrating the use of the Bouncy Castle library |
| EncryptDecrypt | An example of a simple class to encrypt and decrypt messages |
| Chapter 2 | PDF and digital signatures |
| SignHelloWorld | A simple example of adding a visible signature to a document |
| SignHelloWorldWithTempFile | Signing a document using a temporary file to avoid OutOfMemoryExceptions with large PDFs |
| SignEmptyField | Signing an empty text field with iText |
| CreateEmptyField | Creating an empty text field with iText |
| CustomAppearance | Creating a custom appearance for the signature by adding a grey background |
| SignatureAppearance | Creating custom text, custom fonts and using right-to-left writing in a signature |
| SignatureAppearances | Adding a custom image |
| SignatureMetadata | Adding metadata to the signature dictionary |
| SignatureTypes | Ordinary (approval) and Certification (author) signatures |
| SequentialSignatures | Sequential signatures in PDFs |
| SignatureWorkflow | An example where multiple signatures are required |
| LockFields | Locking fields and documents after signing |
| Chapter 3 | Certificate Authorities, certificate revocation and time stamping |
| SignWithCAcert | Signing a document with a PKCS12 file from the CAcert Certificate Authority |
| GetCrlUrl | Getting the Certificate Revocation List (CRL) URLs from a certificate chain |
| SignWithCRLDefaultImp | Using the default CrlClient implementation |
| SignWithCRLOnline | Getting the CRL online |
| SignWithCRLOffline | Creating a CrlClient using an offline copy of the CRL |
| GetOcspUrl | Fetching the Online Certificate Status Protocol (OCSP) URL from a certificate |
| SignWithOCSP | Signing a document with the OCSP |
| GetTsaUrl | Extracting a Time Stamping Authority (TSA) URL from a certificate |
| SignWithTSA | Signing a document with TSAClientBouncyCastle, an implementation of TSAClient |
| SignWithTSAEvent | Adding an event to a TSAClientBouncyCastle instance |
| SignWithToken | Signing a document with a USB token using Microsoft CryptoAPI (MSCAPI) - currently only available for Java |
| SignWithEstimatedSize | Estimating the size in bytes of the signature content |
| Chapter 4 | Creating signatures externally |
| SignWithPKCS11HSM | Signing a document with PKCS#11 using a Hardware Security Module (HSM) - currently only available for Java |
| SignWithPKCS11USB | Signing a document with PKCS#11 using a USB token - currently only available for Java |
| SignWithPKCS11SC | Signing a document with PKCS#11 using a BEID - currently only available for Java |
| ClientServerSigning | Signing a document on the client using a signature created on the server |
| ServerClientSigning | Signing a document on the server using a signature created on the client |
| DeferredSigning | Signing a document by creating a blank signature container, creating a signature appearance on the server and getting a hash to send to the client (deferred signing) |
| Chapter 5 | Validation of signed documents |
| SignatureIntegrity | Checking the validity of a signature |
| SignatureInfo | Retrieving information from a signature |
| CertificateValidation | Validating the certificates of a signature |