Étant donné un message en texte brut et une clé numérique, chiffrer/déchiffrer le texte donné à l'aide de l'algorithme Rail Fence.
Le chiffre de clôture ferroviaire (également appelé chiffre en zigzag) est une forme de chiffre de transposition. Il tire son nom de la manière dont il est codé.
Exemples :
Encryption
Input : 'GeeksforGeeks '
Key = 3
Output : GsGsekfrek eoe
Decryption
Input : GsGsekfrek eoe
Key = 3
Output : 'GeeksforGeeks '
Encryption
Input : 'defend the east wall'
Key = 3
Output : dnhaweedtees alf tl
Decryption
Input : dnhaweedtees alf tl
Key = 3
Output : defend the east wall
Encryption
Input : 'attack at once'
Key = 2
Output : atc toctaka ne
Decryption
Input : 'atc toctaka ne'
Key = 2
Output : attack at once
Cryptage
string.comparer c#
Dans un chiffre de transposition, l'ordre des alphabets est réorganisé pour obtenir le texte chiffré.
- Dans le chiffre de clôture ferroviaire, le texte brut est écrit vers le bas et en diagonale sur les rails successifs d'une clôture imaginaire.
- Lorsque nous atteignons le rail inférieur, nous montons en diagonale après avoir atteint le rail supérieur, la direction change à nouveau. Ainsi les alphabets du message sont écrits en zigzag.
- Une fois chaque alphabet écrit, les lignes individuelles sont combinées pour obtenir le texte chiffré.
Par exemple, si le message est « GeeksforGeeks » et que le nombre de rails = 3, alors le chiffre est préparé comme suit :
chaîne divisée java
Décryptage
Comme nous l'avons vu précédemment, le nombre de colonnes dans le chiffrement rail fence reste égal à la longueur du message en texte brut. Et la clé correspond au nombre de rails.
- La matrice ferroviaire peut donc être construite en conséquence. Une fois que nous avons la matrice, nous pouvons déterminer les endroits où les textes doivent être placés (en utilisant la même manière de se déplacer alternativement en diagonale de haut en bas).
- Ensuite, nous remplissons la ligne de texte chiffré. Après l'avoir rempli, nous parcourons la matrice en zigzag pour obtenir le texte original.
Mise en œuvre:
Soit texte chiffré = 'GsGsekfrek eoe' et clé = 3
- Nombre de colonnes dans la matrice = len (texte chiffré) = 13
- Nombre de lignes = clé = 3
Par conséquent, la matrice originale sera de 3*13, marquant maintenant les endroits avec le texte comme '*', nous obtenons
java attraper essayer
* _ _ _ * _ _ _ * _ _ _ *
_ * _ * _ * _ * _ * _ *
_ _ * _ _ _ * _ _ _ * _
Vous trouverez ci-dessous un programme pour crypter/déchiffrer le message en utilisant l'algorithme ci-dessus.
// C++ program to illustrate Rail Fence Cipher // Encryption and Decryption #include
// Java program to illustrate Rail Fence Cipher // Encryption and Decryption import java.util.Arrays; class RailFence { // function to encrypt a message public static String encryptRailFence(String text int key) { // create the matrix to cipher plain text // key = rows length(text) = columns char[][] rail = new char[key][text.length()]; // filling the rail matrix to distinguish filled // spaces from blank ones for (int i = 0; i < key; i++) Arrays.fill(rail[i] 'n'); boolean dirDown = false; int row = 0 col = 0; for (int i = 0; i < text.length(); i++) { // check the direction of flow // reverse the direction if we've just // filled the top or bottom rail if (row == 0 || row == key - 1) dirDown = !dirDown; // fill the corresponding alphabet rail[row][col++] = text.charAt(i); // find the next row using direction flag if (dirDown) row++; else row--; } // now we can construct the cipher using the rail // matrix StringBuilder result = new StringBuilder(); for (int i = 0; i < key; i++) for (int j = 0; j < text.length(); j++) if (rail[i][j] != 'n') result.append(rail[i][j]); return result.toString(); } // This function receives cipher-text and key // and returns the original text after decryption public static String decryptRailFence(String cipher int key) { // create the matrix to cipher plain text // key = rows length(text) = columns char[][] rail = new char[key][cipher.length()]; // filling the rail matrix to distinguish filled // spaces from blank ones for (int i = 0; i < key; i++) Arrays.fill(rail[i] 'n'); // to find the direction boolean dirDown = true; int row = 0 col = 0; // mark the places with '*' for (int i = 0; i < cipher.length(); i++) { // check the direction of flow if (row == 0) dirDown = true; if (row == key - 1) dirDown = false; // place the marker rail[row][col++] = '*'; // find the next row using direction flag if (dirDown) row++; else row--; } // now we can construct the fill the rail matrix int index = 0; for (int i = 0; i < key; i++) for (int j = 0; j < cipher.length(); j++) if (rail[i][j] == '*' && index < cipher.length()) rail[i][j] = cipher.charAt(index++); StringBuilder result = new StringBuilder(); row = 0; col = 0; for (int i = 0; i < cipher.length(); i++) { // check the direction of flow if (row == 0) dirDown = true; if (row == key - 1) dirDown = false; // place the marker if (rail[row][col] != '*') result.append(rail[row][col++]); // find the next row using direction flag if (dirDown) row++; else row--; } return result.toString(); } // driver program to check the above functions public static void main(String[] args) { // Encryption System.out.println('Encrypted Message: '); System.out.println( encryptRailFence('attack at once' 2)); System.out.println( encryptRailFence('GeeksforGeeks ' 3)); System.out.println( encryptRailFence('defend the east wall' 3)); // Now decryption of the same cipher-text System.out.println('nDecrypted Message: '); System.out.println( decryptRailFence('atc toctaka ne' 2)); System.out.println( decryptRailFence('GsGsekfrek eoe' 3)); System.out.println( decryptRailFence('dnhaweedtees alf tl' 3)); } } // This code is contributed by Jay
# Python3 program to illustrate # Rail Fence Cipher Encryption # and Decryption # function to encrypt a message def encryptRailFence(text key): # create the matrix to cipher # plain text key = rows # length(text) = columns # filling the rail matrix # to distinguish filled # spaces from blank ones rail = [['n' for i in range(len(text))] for j in range(key)] # to find the direction dir_down = False row col = 0 0 for i in range(len(text)): # check the direction of flow # reverse the direction if we've just # filled the top or bottom rail if (row == 0) or (row == key - 1): dir_down = not dir_down # fill the corresponding alphabet rail[row][col] = text[i] col += 1 # find the next row using # direction flag if dir_down: row += 1 else: row -= 1 # now we can construct the cipher # using the rail matrix result = [] for i in range(key): for j in range(len(text)): if rail[i][j] != 'n': result.append(rail[i][j]) return('' . join(result)) # This function receives cipher-text # and key and returns the original # text after decryption def decryptRailFence(cipher key): # create the matrix to cipher # plain text key = rows # length(text) = columns # filling the rail matrix to # distinguish filled spaces # from blank ones rail = [['n' for i in range(len(cipher))] for j in range(key)] # to find the direction dir_down = None row col = 0 0 # mark the places with '*' for i in range(len(cipher)): if row == 0: dir_down = True if row == key - 1: dir_down = False # place the marker rail[row][col] = '*' col += 1 # find the next row # using direction flag if dir_down: row += 1 else: row -= 1 # now we can construct the # fill the rail matrix index = 0 for i in range(key): for j in range(len(cipher)): if ((rail[i][j] == '*') and (index < len(cipher))): rail[i][j] = cipher[index] index += 1 # now read the matrix in # zig-zag manner to construct # the resultant text result = [] row col = 0 0 for i in range(len(cipher)): # check the direction of flow if row == 0: dir_down = True if row == key-1: dir_down = False # place the marker if (rail[row][col] != '*'): result.append(rail[row][col]) col += 1 # find the next row using # direction flag if dir_down: row += 1 else: row -= 1 return(''.join(result)) # Driver code if __name__ == '__main__': print(encryptRailFence('attack at once' 2)) print(encryptRailFence('GeeksforGeeks ' 3)) print(encryptRailFence('defend the east wall' 3)) # Now decryption of the # same cipher-text print(decryptRailFence('GsGsekfrek eoe' 3)) print(decryptRailFence('atc toctaka ne' 2)) print(decryptRailFence('dnhaweedtees alf tl' 3)) # This code is contributed # by Pratik Somwanshi
using System; class GFG_RailFence { // function to encrypt a message public static string EncryptRailFence(string text int key) { // create the matrix to cipher plain text // key = rows length(text) = columns char[] rail = new char[key text.Length]; // filling the rail matrix to distinguish filled // spaces from blank ones for (int i = 0; i < key; i++) for (int j = 0; j < text.Length; j++) rail[i j] = 'n'; bool dirDown = false; int row = 0 col = 0; for (int i = 0; i < text.Length; i++) { // check the direction of flow // reverse the direction if we've just // filled the top or bottom rail if (row == 0 || row == key - 1) dirDown = !dirDown; // fill the corresponding alphabet rail[row col++] = text[i]; // find the next row using direction flag if (dirDown) row++; else row--; } // now we can construct the cipher using the rail // matrix string result = ''; for (int i = 0; i < key; i++) for (int j = 0; j < text.Length; j++) if (rail[i j] != 'n') result += rail[i j]; return result; } // This function receives cipher-text and key // and returns the original text after decryption public static string DecryptRailFence(string cipher int key) { // create the matrix to cipher plain text // key = rows length(text) = columns // create the matrix to cipher plain text // key = rows length(text) = columns char[] rail = new char[key cipher.Length]; // filling the rail matrix to distinguish filled // spaces from blank ones for (int i = 0; i < key; i++) for (int j = 0; j < cipher.Length; j++) rail[i j] = 'n'; // to find the direction bool dirDown = true; int row = 0 col = 0; // mark the places with '*' for (int i = 0; i < cipher.Length; i++) { // check the direction of flow if (row == 0) dirDown = true; if (row == key - 1) dirDown = false; // place the marker rail[row col++] = '*'; // find the next row using direction flag if (dirDown) row++; else row--; } // now we can construct the fill the rail matrix int index = 0; for (int i = 0; i < key; i++) for (int j = 0; j < cipher.Length; j++) if (rail[i j] == '*' && index < cipher.Length) rail[i j] = cipher[index++]; // create the result string string result = ''; row = 0; col = 0; // iterate through the rail matrix for (int i = 0; i < cipher.Length; i++) { // check the direction of flow if (row == 0) dirDown = true; if (row == key - 1) dirDown = false; // place the marker if (rail[row col] != '*') result += rail[row col++]; // find the next row using direction flag if (dirDown) row++; else row--; } return result; } // driver program to check the above functions public static void Main() { // Encryption Console.WriteLine('Encrypted Message: '); Console.WriteLine(EncryptRailFence('attack at once' 2)); Console.WriteLine( EncryptRailFence('GeeksforGeeks ' 3)); Console.WriteLine( EncryptRailFence('defend the east wall' 3)); // Now decryption of the same cipher-text Console.WriteLine('nDecrypted Message: '); Console.WriteLine( DecryptRailFence('atc toctaka ne' 2)); Console.WriteLine( DecryptRailFence('GsGsekfrek eoe' 3)); Console.WriteLine( DecryptRailFence('dnhaweedtees alf tl' 3)); } }
// function to encrypt a message function encryptRailFence(text key) { // create the matrix to cipher plain text // key = rows text.length = columns let rail = new Array(key).fill().map(() => new Array(text.length).fill('n')); // filling the rail matrix to distinguish filled // spaces from blank ones let dir_down = false; let row = 0 col = 0; for (let i = 0; i < text.length; i++) { // check the direction of flow // reverse the direction if we've just // filled the top or bottom rail if (row == 0 || row == key - 1) dir_down = !dir_down; // fill the corresponding alphabet rail[row][col++] = text[i]; // find the next row using direction flag dir_down ? row++ : row--; } // now we can construct the cipher using the rail matrix let result = ''; for (let i = 0; i < key; i++) for (let j = 0; j < text.length; j++) if (rail[i][j] != 'n') result += rail[i][j]; return result; } // function to decrypt a message function decryptRailFence(cipher key) { // create the matrix to cipher plain text // key = rows text.length = columns let rail = new Array(key).fill().map(() => new Array(cipher.length).fill('n')); // filling the rail matrix to mark the places with '*' let dir_down = false; let row = 0 col = 0; for (let i = 0; i < cipher.length; i++) { // check the direction of flow if (row == 0) dir_down = true; if (row == key - 1) dir_down = false; // place the marker rail[row][col++] = '*'; // find the next row using direction flag dir_down ? row++ : row--; } // now we can construct the rail matrix by filling the marked places with cipher text let index = 0; for (let i = 0; i < key; i++) for (let j = 0; j < cipher.length; j++) if (rail[i][j] == '*' && index < cipher.length) rail[i][j] = cipher[index++]; // now read the matrix in zig-zag manner to construct the resultant text let result = ''; row = 0 col = 0; for (let i = 0; i < cipher.length; i++) { // check the direction of flow if (row == 0) dir_down = true; if (row == key - 1) dir_down = false; // place the marker if (rail[row][col] != '*') result += rail[row][col++]; // find the next row using direction flag dir_down ? row++ : row--; } return result; } // driver program to check the above functions // Encryption console.log(encryptRailFence('attack at once' 2)); console.log(encryptRailFence('GeeksforGeeks' 3)); console.log(encryptRailFence('defend the east wall' 3)); // Now decryption of the same cipher-text console.log(decryptRailFence('GsGsekfrek eoe' 3)); console.log(decryptRailFence('atc toctaka ne' 2)); console.log(decryptRailFence('dnhaweedtees alf tl' 3));
Sortir
atc toctaka ne GsGsekfrek eoe dnhaweedtees alf tl GeeksforGeeks attack at once defend the east wall
Complexité temporelle : O(ligne * colonne)
Espace auxiliaire : O(ligne * colonne)
Références :
https://en.wikipedia.org/wiki/Rail_fence_cipher
Cet article est rédigé par Ashutosh Kumar