Network Security: Lab#4-1E-mail Security

J. H. WangDec. 3, 2013

Objectives

• To learn to use e-mail security tools– PGP

• To learn the availability of email security libraries– S/MIME– DKIM

Packages & Libraries in this Lab

• Packages– GPG4win: for Windows

• Libraries– OpenDKIM

Experiment Scenario

• Signing/verification of files using certificates– Create a new certificate– Encrypt/sign the file “original.txt” into another file

“enc.txt” (using sender’s certificate)– Then, we decrypt/verify it and get another file

“dec.txt” (using sender’s certificate), and check if the decrypted file is the same as the original file

• Sending/receiving e-mails with certificates– Set up email account– Read mails– Send mails

GnuPG Privacy Guard

• Homepage: http://www.gnupg.org/• Version:

– 1.4.15 (portable standalone version) – 2.0.22 (enhanced version, harder to build)

• Platforms: Linux/FreeBSD/Windows/MacOS X

• An implementation of OpenPGP• Installation steps

– (skipped)

GPG4win

• Homepage: http://www.gpg4win.org/ • Latest version: 2.2.1• OpenPGP: an open standard for e-

mail security (RFC 4880) – S/MIME also included

• Installation steps:– Simply follow the instructions on screen

Other Tools Included in GPG4win

• Kleopatra: GnuPG certificate manager– New certificate– Encrypting/Signing a file– Decrypting/Verifying a file

• Claws Mail: a mail reader– Setting up your mail account– Reading mails– Sending mails

Microsoft Outlook Support in GPG4win

• PGP for Outlook– GpgOL 1.0 can support OpenPGP and

S/MIME

Configuring Outlook for S/MIME

• Configure Your Personal Email Certificates• Send a Signed Message• Read a Signed Message• Check the Credentials of a Signed

Message• Send an Encrypted Message• Read an Encrypted Message• Get Certificates for Other Users

OpenDKIM• Homepage: http://www.opendkim.org/

– Latest version: opendkim 2.8.4– C library for DKIM service: libmilter– Also a milter-based filter application: opendkim

• Can plug in to any milter-based MTAs: Sendmail, PostFix

• An open source implementation for IETF DKIM standard (RFC 6376) based on dkim-milter from Sendmail– Library: libdkim – Milter: dkim-milter 2.8.3 (plugins to sendmail)

• Also includes implementations of– ADSP (Author Domain Signing Practises): RFC 5617– VBR (Vouch by Reference): RFC 5518

Configuration and Installation

• Compilation of opendkim– Download opendkim-2.8.4.tar.gz– tar -xzvf opendkim-2.8.4.tar.gz – cd opendkim-2.8.4– ./configure– make– make install

• Configuration of opendkim– For signing and verification

• Install opendkim and configure your MTA

Summary

• Email security– PGP– S/MIME– DKIM