Encryption algorithm in C.
Harvard CS50 course exercise.
To compile you must run make substitution or clang -ggdb3 -O0 -std = c11 -Wall -Werror -Wextra -Wno-sign-compare -Wno-unused-parameter -Wno-unused-variable -Wshadow substitution.c - lcrypt -lcs50 -lm -o substitution.
You must put a key of 26 non-repeated characters in the argument, it can be uppercase or lowercase.
Example:
$ ./substitution VchPRZGJnTLsKFBDqWAXeUYMOi
plaintext: Hello, World!
ciphertext: Jrssb, Ybwsp!