 Data Security Manual

 (c) 1995-1996 by: MaeDae Enterprises

5805 Prospero Road

Peyton, CO 80831 USA

Voice: (719) 683-3860   FAX: (719) 683-5199

This data security manual provides information on several security related areas.  In particular, it concentrates on areas related to helping you in the secure use of your small computer.  To get the most out of our security related products you need to have a basic understanding of what data security is.  To aid you in this, we have provided the following information.

Security Topics:

What is data security?

Encryption techniques

Key management

Electronic file transfer

Archives and encryption

USA security policy

Security terms defined

Additional reading


What is data security?

Data security is basically protecting the data you use with your computer.  This can be accomplished through access control methods like locked computer rooms, security guards, and safes.  It can also be through encryption, the scrambling of the data so no one will be able to figure out what the data really is.  We concentrate on encryption for this tutorial.

As you know from the television and newspapers. as networks proliferate so do thieves and the need for data security increases.  The world in the past has largely depended on physical security such as safes and locks.  Computers are rapidly eroding the possibility of physical security (wherever a modem is connected to a phone line).  Laws will be passed, but in the final result, honesty depends on good security.  All the ministrations of legislators and bureaucrats will have little positive effect on security.  Human nature will win out.  The easier it is to get, the more likely it is to be stolen.  Encryption provides part of the answer to the need for increased security.  It will be especially useful in systems that are open to all users but which have some confidential data.  Instead of complex levels of user verification through passwords, everyone can get the file but only the people with the key can decode the information.  Encryption in its present state is cumbersome and time consuming, but faster computers and better programs can ease this problem.  This is where our products come to the rescue.

Encryption is a fascinating exercise.  One of our basic encryption levels implements a version of the Vernam machine developed at Bell labs in the 1920's.  The original machine used Baudot code on a teletype and performed an exclusive or (XOR) on each character of the message and the key to produce the encrypted character.  The message was decoded by the same machine in the same manner.  The method is considered unbreakable if two conditions are met.  First, the key is longer than the message and second, the key is only used once, sometimes called a one time pad.  Typically the files you will be encrypting are much longer than the key.

NOTE:  If there is any question about the randomness of the encrypted file, you  can encrypt the same file multiple times using different keys.  The true randomness of the key should not matter since the use of more than one key will make decoding the file very difficult, if not impossible.  This process could be repeated until the paranoia of the person was satisfied.


Encryption Techniques

The Data Encryption Standard (DES)

Most encryption schemes are kept secret.  One exception is the Data Encryption Standard (DES), which was issued by the U.S. National Bureau of Standards (NBS).  The National Security Agency (NSA) was intimately involved in the development and acceptance testing of the DES algorithm.

In 1972, the National Bureau of Standards (now called the National Institute for Standards and Testing) asked for proposals for a method to encrypt commercial computer data traffic (just like the data in your PC today).  In 1974, the NBS asked NSA for assistance, since the NBS had received an extremely poor response to their original request for proposals.  NSA has as one of its primary functions the development and breaking of information protection techniques (codes and ciphers).  An algorithm developed by IBM became the DES and was issued by the NBS in 1977.  This provided an approved and secure standard for protecting computer data against possible theft or unauthorized access.

DES performs encryption by working on a block of 64 bits of your data using a 64 bit key (we generate the 64 bit key from the key you supply).  Basically, DES is a substitution cipher.

How well does DES protect your data?  The designers of the DES algorithm maintain that the time needed to decrypt a DES encrypted file makes it unprofitable to use trial and error techniques.  Some estimates to break DES are as high as $200 million to try all 72 quadrillion possible keys.

We chose to implement DES because it is a standard and its ability to protect your data is well documented.  Our goal is to provide you with the best possible software tool for the protection of your sensitive data.

Proprietary Encryption Techniques

Our software provides several layers of encryption as its basic level of data protection.  Our proprietary encryption algorithms provide the industry standard xor, transposition, and substitution forms of encryption.  These are applied to your data, one on top of the other, providing multiple layers of encryption.

It is extremely unlikely that anyone will ever go to the expense to break our proprietary level of encryption in our Encrypt-It.  To eliminate even this small possibility we also support adding the secure DES on top of our proprietary encryption techniques.

Cryptographic Encryption Techniques

Cryptographic techniques provide a very cost effective method of protecting your important data.  There are many computer techniques available today for protecting your sensitive data.  Our encryption products uses the following four basic encryption methods:

1.  Transposition - Changes the natural order of data so that a different order for the characters is used.  It swaps characters within a message to place them in a different order based on the encryption key (text string) you use for encryption.  For example, the clear text phrase - THIS IS A TEST - could become - ISTHA SI  TAEST - after encryption.  You will notice that the characters are the same.  However, their order is totally mixed up or transposed.  This process is repeated during decryption to return the data back to its original state.

2.  Substitution - Substitution is one of the simplest encryption techniques.  It creates a new order for the characters.  For example, the order of the text ABCDEFGHIJKLMNOPQRSTUVWXYZ could be changed to a new order ADMYNZEOFPBQGSRHTUIVWJKXL.  The message - THIS IS A TEST - would become - IEOU OU C IYUI -. This example is over simplified for illustration purposes.  When substitution is used within a computer, all 256 possible characters are used so that it is possible to use the technique on different types of computer files.

3.  Exclusive Or - This is a logic operation used by the computer to manipulate the data at the bit level.  For example, a character which consists of 10011001 (shown as bits) could be encrypted with 1101010 to give you 01001100 when the exclusive or is performed.  When either the data or the key contains a 1, the result is a 1, otherwise it is a 0.  To reverse the process, you exclusive or the encrypted data with the key a second time.  This operation is very easy for computers to perform and is used when only a minimum of protection is required.

4.  Data Encryption Standard (DES) - DES performs its encryption by working on a block of 64 bits of your data using a 64 bit key (we generate the 64 bit key from the key you provide).  DES makes a total of 16 passes through each 8 character (64 bit) block of your data substituting a different character for the one initially there.  As you can guess, DES is practically impossible to break.  To eliminate even that small possibility, cipher block chaining (CBC)) is often used to strengthen DES.  CBC provides an exclusive or encryption layer underneath DES that chains the encryption of the unencrypted data from one 64 bit block to the next.


Key Management

The best data encryption software in the world cannot protect your files if you compromise your key.

Encryption Keys

Secure encryption of your data is our job.  The choice of a good key and protecting the key from compromise is your job.

How do you select a good text key?  Several things should be considered:

1.  Keys should not have many repeating characters.

2.  If they have any pattern to the eye they should not be used.

3.  Keys must be kept secure.

4.  Keys should be as long as practical.

We recommend you use as long a key as possible.  Phrases or short sentences should work well as a key and still be easy to remember.  Spaces may be used in your key, but we recommend not using spaces at the beginning or end of the key.  These spaces are easily forgotten.

Management of the Keys

Distribution and maintenance of keys requires planning if it is to be successful.  Both you and the person you send encrypted files to need to know the key. One way to handle this is to coordinate a key through a trusted avenue -- in person, over secure phone circuits, etc.

Once you have a trusted secure key, generate and encrypt other keys on an as needed basis.  Encrypt the work keys in your trusted secure key and send the encrypted key to the person who will be decrypting your files.  Since the work keys will encrypted, they can be sent through any avenue you want.  You do not have to protect them since they are encrypted.

The person at the end will receive your list of keys and decrypt them using the coordinated private key.  You can now safely switch to the new keys.

This simple concept should make key management much easier for you.

Generating Binary Keys

Encryption routines like DES require a key consisting of a sequential number of bits.  There are several ways to translate a phrase like - my dog is brown - into a binary key.  One easy way to generate this key is to calculate the cyclic redundancy check (CRC) of the phrase generating a 16 bit or 32 bit binary signature for the entire phrase.

You could then use this signature as the first part of the binary key.  The rest of the binary key could be made up of the first few characters of the textual phrase.  That way you could have a binary key that varied with the textual phrase but was much smaller.

Our Windows Encryption Toolkit provides a CRC function to help you take advantage of this approach to binary key generation.


Electronic File Transfer

Many products, like our Encrypt-It, build extensive file validation checks into the file structure of the encrypted file.  If any character of the encrypted data is EVER changed, you are notified!   The implications are discussed in the following paragraphs.

Our extensive checks means you can have complete confidence that the decrypted data is ALWAYS exactly what you started with.  However, there is a drawback.  You need to be aware of the limitations of the electronic transfer medium you use.   If the file transfer alters the original file in ANY way, Encrypt-It will flag this as an attempt to alter your data.  In essence it really is, but it may just reflect the limitations of the electronic transfer medium you are using.

When you transfer files by floppy diskette, preservation of the original size and contents without error are virtually guaranteed.  The same cannot be said about electronic transfer of data via bulletin boards and information services like CompuServe or GEnie.  Our suggestions for electronic file transfer are:

1.  Consider using our email conversion routines if the file must go through an email type service.  Our email file format builds in additional error checking plus restoration of the filename, date, time, etc.

2.  Use ZModem protocol whenever possible.  Kermit may also maintain the correct file size, but we are unsure of other protocols.  A problem with XModem is that it adds bytes to round the file size up to the next higher block size.  Check your file transfer protocol to make sure it does not add additional characters to pad the transferred data out to a standard block size.

3.  ALWAYS use error correction if it is an option.  Implementations of ZModem frequently offer the option of using a 32 bit CRC, use this whenever possible.  If a file is ever altered during transfer, our Encrypt-It will flag it as a modification of your data!  This includes any attempt to add or delete characters!

We want to provide you with the best possible protection for your data!  If our checks seem like we are going overboard, then we have accomplished our goal.  Our goal is total protection for your sensitive data.  Nothing less is acceptable.


Archives and Encryption

Archives like .ZIP and .LZH are frequently used to store files.  This may be done to reduce storage requirements or just to group all the files needed for a given application.  Archives are especially useful when the files are to be transferred electronically.

For best results with archives, first archive your files then encrypt the archive.  Archivers cannot compress encrypted files.  Compression techniques typically rely upon uneven character distribution or repeating patterns in the data to be able to accomplish their function.  After encryption, the data has an even character distribution without any repeating patterns.

Archives can also be used to get around limitations of  the electronic file transfer protocols.  Some of the protocols add bytes which alter  your data.  If you archive the encrypted file first, transfer the archive, and then break it out, you will have gotten around these problems.  This may in some cases mean that you archive all your files, encrypt the archive, and then archive the encrypted file to get around the protocol limitations.


USA Security Policy

Overview of USA Regulations

The USA government, in its usual cryptic fashion, classifies encryption software under the International Traffic in Arms Regulations (ITAR).  The ITAR does not deal well with technical data that can exist in many different forms and flow across national boundaries on BBSs, Internet, and other electronic services.  In fact, some of the best source code for encryption techniques, regulated by the ITAR, frequently originates outside the USA.  This source code can be imported via electronic means, built into commercially competitive products, and then cannot be exported to the world-wide marketplace.  Examples of this are the DES and IDEA (from Switzerland) encryption techniques which are available in commercial products throughout the world, but cannot be exported outside the USA and Canada.

ITAR currently makes a distinction on what type of encryption software can be exported primarily based on the complexity of the encryption algorithm (sometimes linked to the number of bits in the encryption key).  It is tied back to whether the US government feels they can break the encryption technique given their super computer resources.  Basically, it goes something like this:

- XOR, transposition, substitution, and the like can be freely exported.

- RSA 40 bits or less can be freely exported.

- RSA 41-64 bits cannot be exported unless you build in a back door and give the government the key.

- RSA greater than 64 bits cannot be exported.

- DES cannot be exported unless you build in a back door and give the government the key.

- Other encryption schemes like the 128 bit IDEA cannot be exported.

Use of Encryption Software in USA Government

To the best of our knowledge, no software is authorized for the encryption of classified information (Confidential, Secret, and Top Secret) in the USA.  Only hardware encryption devices are approved for the processing of classified data.  Software encryption can be used only for the encryption of For Official Use Only (FOUO) data such as base telephone books.

Notes:

1.  In order to comply with USA DES export restrictions, we will NOT sell any DES enabled encryption product outside the USA and Canada.  All other orders will be filled with the simpler proprietary encryption versions.  We have chosen to eliminate all back doors in our DES products so the USA regulations prohibit us from exporting them.

2.  The USA is currently working on security policies (as always).  The above general export guidelines are subject to immediate change as the USA changes their minds.


Security Terms Defined

Terms used when dealing with encryption may be a little confusing.  They are terms frequently used when discussing cryptography.  We picked the most important ones and defined them for you here.

Cipher -- Any technique, method, or scheme (XOR, substitution, transposition, etc.) used to encrypt and decrypt text, without regard to its linguistic structure.

Cipher Block Chaining (CBC) -- Provides an exclusive or encryption layer underneath DES that chains the encryption of the unencrypted data from one 64 bit block to the next.

Ciphertext -- The unintelligible text, after encrypting it.

Cryptanalysis -- The solving or breaking of codes without knowledge of the key.

Cryptography -- The general study of hiding the meaning of messages and the general techniques used for the hiding.

Data Encryption Standard (DES) -- DES is basically a substitution cipher using a 64 bit block of your data and a 64 bit key.

Decrypting -- The process of  decoding an encrypted or ciphertext file to regain the original information.

Encrypting -- The process of encoding a plaintext file to hide the original information.

Exclusive Or (XOR) - This is an encryption technique that uses  logic computer operations to manipulate the data at the bit level.

Key -- The text used to encrypt or decrypt a file.  Sometimes called a code word or password.  Keys can be simple everyday words or very complex combinations of characters that have no meaning.  Example keys: abc1234, Never:Again, and Buy Bonds.

Plaintext -- The unencrypted or decrypted, readable text.

Substitution - Substitution is one of the simplest encryption techniques.  It creates a new order for the characters.

Transposition - An encryption technique that changes the natural order of data so that a different order for the characters is used.  It swaps characters within a message to place them in a different order based on the encryption key (text string) you use for encryption.


Additional Reading

The books listed below were useful in the development of our security related products.  In particular, Applied Cryptography was very useful in helping to evaluate the protection provided by different encryption techniques.

1.  John Wiley & Sons, Inc., Applied Cryptography, by Bruce Schneier, 1993.

2.  Aegean Park Press, Elements of Cryptanalysis, by William F. Friedman, 1976.

3.  Aegean Park Press, Introduction to the Analysis of the Data Encryption Standard, by Wayne G. Barker, 1991.

4.  Sams Publishing, Top Secret Data Encryption Techniques, by Gilbert Held, 1993.