Years ago, there were numerous competing utilities designed to combine and compress files, both for easy distribution and for security. Each used its own proprietary file format and naturally each claimed to be the best. These days you'll be hard-pressed to find a SEA file or an ARC file, but ZIP files are absolutely ubiquitous. While ZIP support is built into modern versions of Windows, a full-scale ZIP utility offers vastly more power and flexibility for managing these useful files. In addition, SecureZIP Standard Edition for Windows Desktop 12.1 helps you use high-end public-key cryptography to protect and digitally sign your ZIP files and e-mail messages. It will even obtain the necessary digital certificate for you and register it in PKWARE's global repository. Best of all, it's still free for non-commercial use. Do go ahead and get your non-expiring free license soon, because it won't be free forever.

Public Key Primer

Ordinary ZIP file compression is symmetrical—you use the same password to decrypt it as you did to encrypt it. If you're sending someone an encrypted file, you need a secure way to transmit the password. Public key cryptography is asymmetrical. It uses two different keys, one public and one private. There's no way to derive the private key from the public one, so there's no risk in posting the public key where anybody can find it. Someone who wants to send you data securely just looks up your public key and uses it to encrypt the data. On receiving the data you decrypt it with your private key. It's an elegant system, combining security and ease of use.

It works in reverse, too. If you encrypt a file with your private key, anybody can decrypt it with your public key. Pointless? Not at all! The fact that they can decrypt the file proves that it was encrypted using your private key and not modified by anyone else. This type of validation is called a digital signature. SecureZIP 11 made using public key encryption for ZIP files possible. Version 12 makes it easy, as you'll see.—Next: Seamless Certificate Security

Seamless Certificate Security

When you install SecureZIP, it offers to get you a free digital certificate from Comodo, a well-known certificate authority, and the maker of Comodo Firewall. The process is extremely simple; you just follow the prompts and copy a verification code that's sent to the e-mail address you provided. SecureZIP handles installing the certificate locally, making it the default certificate for ZIP file encryption, and registering it with the SecureZIP Global Repository. If you already have an X.509-compatible certificate from some other source you can register it with the global repository too.

The more expensive PGP Desktop works in much the same way. It offers access to its own repository along with the ability to automatically look up your mail recipients and encrypt the message using their public keys, if found. SecureZIP's repository is separate from PGP's, naturally, but it offers the same convenience. And yes, it's possible to encrypt a file or message using multiple public keys, thereby allowing multiple recipients to decrypt it using their personal private keys. You can even add a passphrase—recipients who don't have a certificate will use the passphrase to decrypt the data. That's flexible! As noted, the same technology lets you digitally sign a message or a file to prove that it comes from you and that it hasn't been tampered with.

If you use your certificate to encrypt and store sensitive files on your computer, SecureZIP transparently decrypts them for you. But, be warned, it also transparently decrypts them for anybody who has logged into your Windows account. If there's any possibility someone else might have your Windows logon credentials you might do better to use passphrase encryption for these local files. Also, if you plan to carry encrypted files on a USB drive or other removable media, you must use a passphrase, because when you plug that drive into a different computer your private key won't be available.

Certificates usually expire in a year, for security reasons. SecureZIP will warn when yours is about to expire and help you get a new one. The private key from your expired certificate will still open the corresponding encrypted files, but going forward SecureZIP will use the new key. If by some mischance your private key is compromised or stolen you can revoke it to prevent misuse.—Next: E-mail Integration

E-mail Integration

SecureZIP integrates with Microsoft Outlook to completely automate the process of zipping e-mail attachments and messages so they take less space. The program can also digitally sign the ZIP file, encrypt it, and optionally encrypt the message body. If the recipient also has SecureZIP installed and integrated with Outlook the message body will be decrypted automatically. Others will receive the message as an attachment, along with instructions on how to open it. With version 12.2, expected in July, PKWARE will extend this e-mail integration to Outlook Express and Windows Mail.

An icon in the system tray offers easy control of this feature. You can specify whether you want to zip attachments and whether you want to encrypt or sign the zipped data. Another box controls whether it encrypts the message body. And by simply clicking the icon you can turn the attachment-handling feature off temporarily without losing the individual settings. You can also set the options for the current message using buttons on the SecureZIP toolbar in Outlook or Word (in Office 2007, the SecureZIP ribbon).

All of this action happens after you hit Send, so if the feature is turned off it's already too late. I prefer to let SecureZIP prompt me for what to do with each message—if I don't want to zip or encrypt I simply decline its offer. And since I get a reminder each time I won't accidentally send a sensitive attachment without protection.—Next: Office Integration

Office Integration

SecureZIP now integrates fully with the Microsoft Office programs Word, Excel, and PowerPoint. When you click File | Save As you'll see new options to save a copy as a ZIP file or as an encrypted ZIP file. And when you open the resulting file SecureZIP will offer to open the Office file contained within it. Actually, SecureZIP will make this offer for any ZIP file that contains a single Office file and nothing else. Naturally when you save the document the ZIP file gets updated with your changes.

If you want to crank up the security level a bit, you can configure SecureZIP so that the new menu options save the file itself within a ZIP archive rather than just saving a copy. Newly created files will exist only inside the ZIP file; for old files there's an option to delete the original file non-zipped after saving. You can't reopen such a document from the list of recently used files, but SecureZIP does add an "Open ZIP File" item to the File menu.—Next: The Expected

The Expected

SecureZIP is, of course, a fully functional ZIP file utility, with all the expected features. It can open over a dozen compressed file formats including Microsoft .cab files and Java .jar files. A context menu lets you send files to a new or existing ZIP file directly from Windows Explorer. By setting the proper options you can use it for backup, adding only files that have changed since the last backup. You can set it to split an archive to fit various removable media sizes or archive directly to multiple diskettes, formatting as needed.

The program can save a ZIP file as a self-extracting archive. This is an executable file that, when launched, extracts its contents to a specified location. It can also add links to the Start menu, register file types with Windows, and run a specified program when extraction completes. In short, it's an effective installer for simple programs. I could go on, but the standard ZIP utility features haven't changed significantly since version 11. The big news about version 12 is all in the security realm.

SecureZIP does everything you'd expect from a ZIP archive utility and much more. It makes securing your e-mail attachments and messages simple and brings public key cryptography into every user's reach. Visit the SecureZIP site to get your copy now, as it won't be free forever.

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