Free Software for DOS
Encryption & Encoding

21 Aug 2006

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The IDEA, RIJNDAEL, and Blowfish algorithm private key programs listed here should be the most secure but I make no personal claims. If you want to prevent your mom or little brother from reading your love notes, any encryptor listed here should do the trick. If your mom works for the CIA, or if you intend to send/receive sensitive information over the Net, I'd start at a different web page (e.g., See

Z-Crypt — Small, fast file encryption / decryption program.

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[updated 2005-03-11]

A private key file encryption program – small, fast, and "anonymous." While Z-Crypt does not implement a well-tested cipher, it does combine several features that attempt to ensure the anonymity of encrypted files.

NOTES: Probably sufficient for non-critical needs, but cryptography experts probably wouldn't recommend it for high security uses. Unlike Tiny IDEA, Z-crypt only accepts a 1-word password, not a passphrase. A password must be typed on the command line, or included in a batch file – so there is a risk of it being seen by others. Cautions and quirks: DOS version shouldn't be used on files with Win 9x LFNs (non 8+3). Z-Crypt doesn't distinguish encrypted from decrypted files if you don't enter the proper password – if you enter the wrong password then the file gets encrypted again, rather than announcing that you used a wrong password! Package contains both DOS and OS/2 executables, and source.

Author: Tim Middleton (1995).

1995-10-21: v0.31

Download (82K).

tiny IDEA — Small IDEA file encryptor and decryptor program.

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[updated 2006-03-14]

Tiny IDEA is a 500-byte private key file encryption program that uses the IDEA cipher. It is used to scramble files with a key, such that the original file cannot be recreated without knowledge of the key. Because tiny IDEA overwrites files during encryption, it can also be used to destroy sensitive files. Does not scramble file names.

From the documentation:

IDEA operates on 64-bit data blocks using a 128-bit key. No method of cracking IDEA faster than exhaustive key search (brute force) has been discovered, despite extensive analysis by professional cryptologers. As an example of IDEA's strength, imagine an incredibly fast computer that can brute force a 56-bit DES key in 1 second. This computer would take up to 194 days to crack a 80-bit key, like the one used by the NSA Skipjack cipher, and up to 149745258842898 years to crack a 128-bit IDEA key.

Author: Fauzan Mirza, w/ optimizations by B. Couture and Mark Andreas, UK (1996).

1996-09-18: v3a, b, c.

Download (20K).

For more info go to Robert G. Durnal's site My Privacy and Encryption Links and Files.

TI — A smaller tiny IDEA, with added features.

* * * *

[updated 2004-06-27]

Based on tiny IDEA (above), changes include smaller size (366 bytes), ability to put passphrase on the command line, & more. This distribution includes several variations, with different combinations of features. Note that it is export restricted from the USA.

Author: Mark Andreas, UK (1998).

1998-12-31: v4.

Download (51K).

For more info, go to Robert G. Durnal's site My Privacy and Encryption Links and Files.

TinyFish — 5K Blowfish file encryptor.


[added 1998-09-25]

Designed along the same lines as Tiny IDEA, but uses a Blowfish algorithm. From the docs:

Authors: Anonymous, based on TINYIDEA by Fauzan Mirza. Optimization and documentation by Dutra de Lacerda, Portugal (1998).

Download (10K).

More in these pages from Dutra de Lacerda.

TINYAES — Small RIJNDAEL file encryptor and decryptor.


[added 2001-09-19 updated 2004-12-24]

TINYAES is a tiny (460 bytes) interactive file encryption program that uses the RIJNDAEL 128, 192 or 256-bit key cipher. RIJNDAEL is a winner of NIST's AES (Advanced Encryption Standard) competition. The DOS binary packaged here uses a 128 bit key, but the source can be re-assembled to use other key sizes. Encryption overwrites the original file; the original is recoverable only by decryption.

The encryption key length as distributed in this package is 16 bytes. Because the user input key is hashed, this allows 32 bytes to be input at the passphrase prompt.

        TINYAES + <FILE>         (encrypt)
        TINYAES - <FILE>         (decrypt)
        TINYAES -X<FILE>         (passphrase checking - see docs)

Remarks: Single file encryption (does not accept wildcards) and is interactive (i.e., prompts for a passphrase). Source included.

Author: Robert G. Durnal (2004). Suggested by Dutra de Lacerda.

2004-11-09: v3.12, reassembled.

Download (17K).

For more info, go to Robert G. Durnal's site My Privacy and Encryption Links and Files.

Blowfish-CBC — Blowfish file encryptor.


[added 1998-09-25, updated 2005-07-17]

A private key file encryption program that uses a CBC implementation of the BlowFish algorithm.

          BLW-x86 (E|?|D) <Key> <InputFile> [<OutputFile>]
	       Encrypt    Decrypt           Optional!

	  For Best Protection Use LONG Keys, using '_' as spaces!
	   Cipher files are NOT compressable :: Do it BEFORE EnCrypt!
	    Default extension is 'BFC' :: Original extension is saved
	    Example          Mode        Key         File
	    ~~~~~~~           |           |            |
	 C:\SECRET>  BLW-CBC  E  MyOwn_Secret_Key  myfile.txt  <Enter>

Author: Dutra de Lacerda, Portugal (2001).

16-bit only. Get this if you need to decrypt files that were encrypted by an earlier v1.5. Package includes docs, PAS source.
16-bit and 32-bit (DJGPP build, requires 80386+ and included CWSDPMI), test util, 16-bit version's PAS source, older 16-bit v1.5 (exe only). Recommended for new users.


More in these pages from Dutra de Lacerda.

snow — Conceal text message in an ASCII file.


[added 1998-05-09, updated 1999-01-17]

From the docs:
...snow is used to conceal messages in ASCII text by appending whitespace to the end of lines. Because spaces and tabs are generally not visible in text viewers, the message is effectively hidden from casual observers. And if the built-in encryption is used, the message cannot be read even if it is detected...If a message string or message file are specified on the command-line, snow will attempt to conceal the message in the file infile if specified, or standard input otherwise. The resulting file will be written to outfile if specified, or standard output if not. If no message string is provided, snow attempts to extract a message from the input file. The result is written to the output file or standard output.

If a message (or message file) cannot fit into the host file's available "free space," lines will be appended to the end of the file. An option does exist to adjust the length of lines which increases available message space. Optional encryption of the message is supported using the 64-bit ICE encryption algorithm in 1-bit cipher-feedback mode. Passwords can (theoretically) be up to 1170 characters in length. Simple compression of the message is also possible. Note that the original and message-containing files may differ in size, and there is no special, secure handling of passwords. Unix and Java versions are also available.

Author: Matthew Kwan, Australia (1998).

1998-11-22: v1.1 for 16-bit DOS and Win32 console. Files concealed with encryption using the DOS version can now decrypt output of other versions.


SNOW Home Page.


KeyGen — Auto-generates multiple passphrases; saves to file; configurable.


[added 1998-09-12]

This program quickly generates multiple passphrases and automatically saves them to a user-named file. The program allows you to set options from a menu: Use upper and/or lower case alphabet, and/or numbers, and/or special characters; define passphrase length (10-80 characters); and define number of passphrases generated (1-999). In practice KeyGen only seems to generate a max of 231 (not 999 as advertised) passphrases with length 80. No description of algorithm used, no source.

Author: Zoltán Pupp, Hungary (1997).

1997-12-18: v1.0.

Download (8K).


Also see some larger progs or packages that include uuen/decode: TutordoDOS NavigatorDisplayGenesis Commander

uuencode & uudecode — 7-bit <> 8-bit text converters, ported from Unix.


[added 2004-10-29]

uuencode translates the 8-bit characters of binary files into a 7-bit text format that can be enclosed in email. uudecode reverses the process, converting a mail enclosure to binary format. 32-bit (emx) executables, work under DOS and OS/2.

Author: Adapted by Mark Adler et al. (1990) from Berkeley Unix originals.

Download (41K).

32-bit DOS versions are included in the GNU sharutils package.

UUdeview — UUE, XX, Base 64 (MIME), encode/decode. Decodes BINHEX.

* * * * *

[updated 2004-10-29]

Enview is capable of encoding files into UUE, XX-UUE, and Base 64 (MIME) formats. UUDeview can decode all of these plus the Macintosh BINHEX (*.hqx) format. UUDeview handles sequential and multipart files well. The program runs interactively, allowing one to make decoding decisions (e.g., renaming) based on the contents of the encoded message. Batch processing is also possible. The executable file sizes are a tad large compared to other DOS encode/decode utilities (100K each for encoder and decoder).

Author: Frank Pilhofer, Germany (1997).

Win32 Console

Win32 Console

See the UUDeview Home Page for more information, versions for other OSes & sources.

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