This library serves as support material for C and C++ developpers to get started with TrustInSoft CI.
TrustInSoft CI is an online source code analyzer that continuously detects undefined behaviors in C and C++ programs (i.e. crash, arbitrary code execution, etc.).
It is more powerful than most current solutions, because it can detect the most subtle undefined behaviors, even when applied to well-tested code that has never revealed any problem. It also comes with a powerful debugging interface that helps developers easily find the root cause of undefined behaviors.
The library is based on the Caesar cipher.
The Caesar cipher is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plain text is replaced by a letter some fixed number of positions down the alphabet.
For example, with a fix number 3, the letter A is replaced by D.
Plain text: c a e s a r
Cipher text: f d h v d u
The user provides the string to encrypt as well as the corresponding shifting value, and the same applies for the decrypt version.
The specificity of the caesar_encrypt function is that it always
performs a shift to the right while the caesar_decrypt function
always performs a shift to the left.
/* \brief Encrypt a string with a right shift specified by the user
\param [in] str The string to encrypt
\param [in] d The right shift to perform
\return The pointer to the encrypted string
*/
char *caesar_encrypt(char *str, int d);
/* \brief Decrypt a string with a left shift specified by the user
\param [in] str The string to decrypt
\param [in] d The left shift to perform
\return The pointer to the decrypted string
*/
char *caesar_decrypt(char *str, int d);A test driver has been written to check the functional correctness of the source code:
∀ string str, int d, caesar_decrypt(caesar_encrypt(str, d), d) = str
The test driver performs two tests:
- encrypt and decrypt a string with a negative shift value
- encrypt and decrypt a string with a positive shift value
The two tests aim at covering all the source code and checking the
source code specification (i.e. passing a negative value to
caesar_encrypt should still perform a shift to the right).
$ gcc -I. -fprofile-arcs -ftest-coverage caesar.c main.c && ./a.out
Test 1: Shift with a negative input
Encrypt text 'People of Earth, your attention please'
Result: Shrsoh ri Hduwk/ |rxu dwwhqwlrq sohdvh
Decrypt text 'Shrsoh ri Hduwk/ |rxu dwwhqwlrq sohdvh'
Result: People of Earth, your attention please
Test 2: Shift with a positive input
Encrypt text 'People of Earth, your attention please'
Result: Wlvwsl vm Lhy{o3 �v|y h{{lu{pvu wslhzl
Decrypt text 'Wlvwsl vm Lhy{o3 �v|y h{{lu{pvu wslhzl'
Result: People of Earth, your attention please
$ gcov caesar.c
File 'caesar.c'
Lines executed:100.00% of 17
caesar.c:creating 'caesar.c.gcov'