Pdf Digital signature

example-signature.dart

import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;
import 'package:pdf_crypto/pdf_crypto.dart';
import 'package:printing/printing.dart';

Future<void> main() async {
  runApp(const MyApp('Printing Demo'));
}

class MyApp extends StatelessWidget {
  const MyApp(this.title, {Key? key}) : super(key: key);

  final String title;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text(title)),
        body: PdfPreview(
          build: (format) => _generatePdf(format, title),
        ),
      ),
    );
  }

  Future<Uint8List> _generatePdf(PdfPageFormat format, String title) async {
    final pdf = pw.Document(version: PdfVersion.pdf_1_5, compress: true);
    final font = await PdfGoogleFonts.nunitoExtraLight();

    pdf.addPage(
      pw.Page(
        pageFormat: format,
        build: (context) {
          return pw.Column(
            children: [
              pw.SizedBox(
                width: double.infinity,
                child: pw.FittedBox(
                  child: pw.Text(title, style: pw.TextStyle(font: font)),
                ),
              ),
              pw.SizedBox(height: 20),
              pw.Flexible(child: pw.FlutterLogo()),
              pw.Signature(
                name: 'Signature',
                value: PdfSign.pkcs7Rsa(
                  permissions: PdfSignPerms.none,
                  digest: HashAlgorithm.sha512,
                  privateKey: PdfSign.pemPrivateKey(
                    privateKey,
                  )!,
                  issuer: X509.fromPem(certificate),
                  chain: [
                    X509.fromPem(ca),
                  ],
                ),
                child: pw.Container(
                  margin: const pw.EdgeInsets.all(20),
                  padding: const pw.EdgeInsets.all(10),
                  decoration: pw.BoxDecoration(
                    border: pw.Border.all(width: 2, color: PdfColors.amber),
                    borderRadius:
                        const pw.BorderRadius.all(pw.Radius.circular(10)),
                  ),
                  child: pw.Text(
                    'Document Digitally Signed on ${DateTime.now()}',
                  ),
                ),
              ),
            ],
          );
        },
      ),
    );

    return pdf.save();
  }

  static const privateKey = '''
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----
''';

  static const certificate = '''
-----BEGIN CERTIFICATE-----
MIIDrTCCApWgAwIBAgIBKTANBgkqhkiG9w0BAQUFADBwMQswCQYDVQQGEwJDQTEQ
MA4GA1UECAwHT250YXJpbzEQMA4GA1UEBwwHVG9yb250bzENMAsGA1UECgwERGVt
bzEcMBoGCSqGSIb3DQEJARYNZGVtb0BkZW1vLmNvbTEQMA4GA1UEAwwHRGVtbyBD
QTAeFw0yMjAzMjUxMjIzNDFaFw0yMzAzMjUxMjIzNDFaMHQxCzAJBgNVBAYTAkNB
MRAwDgYDVQQIDAdPbnRhcmlvMRAwDgYDVQQHDAdUb3JvbnRvMQ0wCwYDVQQKDARE
ZW1vMRwwGgYJKoZIhvcNAQkBFg1kZW1vQGRlbW8uY29tMRQwEgYDVQQDDAtEZW1v
IFNJR04gMTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAND1VkOKJ6Ml
K2Qk0t+AyLrt+FmtvDlmsx6waXzf5ueD6+xNBJfozw5t5B+Zi291tvfqcR4qBlME
VbXYbf628VJ4JF8RdpznClk+YJ1IFXag5ITk71LhdXce3cCBhnEBB/7ldX1tqBml
ZYcGHXNZ4lFKVlEbVK7CgxNFKGE4ryHTQF0WVm5/HDH4avSjUm5MNjYri8d+AP0v
cQWXe/0mPJg+yFrcPHYtt7uPj2/bc4RUYtQg5+QTnWvKdBotdgyjEv+vooHUcnBF
wSjfvejwsGr2KQNDgzzuSl5KI4ed0WCdDylLUIqg30jnrpNpe7GR/lInuKyaOEzC
NgnjOgXgFCsCAwEAAaNOMEwwDAYDVR0TAQH/BAIwADAOBgNVHQ8BAf8EBAMCB4Aw
LAYDVR0fBCUwIzAhoB+gHYYbaHR0cDovL2NlcnQuZDQxNy5wdy9jcmwucGVtMA0G
CSqGSIb3DQEBBQUAA4IBAQDCKnmerQ3Agxa105HXct/pIQX3GnJkSeUCPOMcxAvt
sPFC0Fbg4tR0039PwNoeqXx963Yhb2ivhysJhKBYU8hmskBf90OAzbZsAF1mD+e1
3UxbU+GphUU/WWrgM7NTWaDAU33e2ru/rjebzoHA43bQ9IXaP4BfZ640/iNzlT1V
Z/+aaQsTIkkg+tQnt0FXcVWZL3Xp4YodY62/7nk9Zy1mOOvIR1sLTaBnyTNcbDWx
/uLVFshX2rf03d94rtJmNYILw7/hMQCWixtUcMUFIjQXFgF137IqCBgP+GBo+K6O
c6A4KILknMe2HdEV5QDRhr/B6ap9QvmFDw6SFIuzPUv1
-----END CERTIFICATE-----
''';

  static const ca = '''
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
''';
}