ATBASH is a FORTRAN90 library which applies the Atbash substitution cipher to a string of text.
The Atbash cipher replaces each character by its reverse element in the alphabet. In particular 'A' becomes 'Z', 'B' becomes 'Y' and so on. Case is respected. Nonalphabetic characters are unchanged. The Atbash cipher is symmetric, so applying it to an enciphered string returns the original string.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
ATBASH is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.
CAESAR, a FORTRAN90 library which can apply a Caesar Shift Cipher to a string of text.
CHRPAK, a FORTRAN90 library which works with characters and strings.
FILUM, a FORTRAN90 library which can work with information in text files.
ROT13, a FORTRAN90 library which can encipher a string using the ROT13 cipher for letters, and the ROT5 cipher for digits.
You can go up one level to the FORTRAN90 source codes.