Before you get too carried away by the capabilities of off the shelf character recognition, read Phil Karn's experience trying to produce a working DES program from the pages of Applied Cryptography. It was easier than writing it himself, but it was still far from a turnkey operation. This is from <URL: http://www.qualcomm.com/people/pkarn/export/karndecl.html >
5. I began by first photocopying, on a standard office photocopier, the 18 pages containing the Triple DES source code listing from Part V of the Book. This took about 5 minutes. Second, I scanned in the 18 sheets on a Macintosh Quadra 610 computer system equipped with an HP ScanJet II flatbed scanner and Omnipage Professional optical character recognition (OCR) software. The computer, scanner, and software are all readily available through normal consumer computer supply channels. The total scanning process took about one and a half hours. About an hour of this time was spent learning to use the scanning system and conducting trial runs, as I had only used it briefly some time ago. The actual scan of the 18 pages took about 15-20 minutes. Third, I transferred the resulting machine-readable file from the Macintosh to my own personal computer and brought it up under GNU EMACS, a popular and widely available text editing program that I have used for many years. In EMACS I compared, by eye, the scanned file displayed on my screen against the printed listing in the Book. I began correcting the scanner's many errors, such as mistaking the digit '0' for the letter 'O' or mistaking the vertical bar '|' for the letter 'I'.
6. After manually correcting those errors noticed through visual comparison with the Book, I invoked the "C" language compiler on the (partially) corrected file. The compiler immediately pointed out additional errors I had overlooked in my visual inspection so I could also correct them by reference to the Book. I also noticed several errors in the listing printed in the Book. However, the programmer's intentions were obvious from the context of each error and were easily fixed. About fifty minutes later, I successfully compiled the file without error.
7. The fourth step was to write a small test program to execute the DES code with the test vectors given at the end of the source code listing. This trivial program took less than 5 minutes to write. Unfortunately, the test did not succeed, meaning that at least one error went undetected by the compiler in either the code as printed in the Book or as scanned. Scrutinizing the code more closely, I quickly found another error in the printed version that was easily corrected. However, it still did not produce correct results. After about an hour of searching, I finally located the error in a list of numbers in a table -- another error in the printed version. By reference to the DES algorithm description in the first part of the Book, which includes the correct numbers in tabular form, I found and corrected the error.
8. At this point the test finally succeeded, so I knew I had a correct program. However, to increase my confidence further I tried a few other DES test vectors that were not included in the source code, but were openly published by the US National Institute of Standards and Technology (NIST). All passed. At this point it was beyond doubt that I had a correct, working copy of the DES source code identical to that on the Disk with all errors removed, including those printed in the Book as well as those added by the scanning process.
9. Finally, in about 40 minutes I wrote and debugged a "driver" program analogous to that included in the Crowell declaration. This driver program takes a sample plaintext file, encrypts it, displays the encrypted file in hexadecimal and then decrypts it.