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Objective-C实现单板密码算法
为了实现单板密码（Playfair Cipher）算法，我们首先需要设置一个密钥，并将其扩展成一个3x3的矩阵。以下是Objective-C代码实现的详细步骤：
以下是完整的Objective-C代码实现：
#import@interface PlayfairCipher : NSObject@property (nonatomic, strong) NSString *keyword;@end@implementation PlayfairCipher- (NSString *)encrypt:(NSString *)plaintext withKey:(NSString *)key { // 1. 密钥扩展 // 创建一个3x3的二维数组来存储扩展后的密钥 NSMutableArray *keyMatrix = [NSMutableArray new]; for (int i = 0; i < 3; i++) { [keyMatrix addObject:[NSMutableArray new]]; } // 将密钥字符串填充到密钥矩阵中 [self fillKeyMatrix:key withMatrix:keyMatrix]; // 2. 生成密钥对应的排列矩阵 // 创建一个3x3的排列矩阵 NSMutableArray *permutationMatrix = [NSMutableArray new]; for (int i = 0; i < 3; i++) { [permutationMatrix addObject:[NSMutableArray new]]; } // 生成排列矩阵 [self generatePermutationMatrix:keyMatrix permutationMatrix:permutationMatrix]; // 3. 生成完整的密码表 // 创建一个3x3的密码表 NSMutableArray *cipherTable = [NSMutableArray new]; for (int i = 0; i < 3; i++) { [cipherTable addObject:[NSMutableArray new]]; } // 生成密码表 [self generateCipherTable:permutationMatrix cipherTable:cipherTable]; // 4. 加密过程 // 将明文转换为密文 NSMutableArray *plaintextChars = [plaintext charactersOfString]; NSMutableArray *cipherText = [NSMutableArray new]; for (int i = 0; i < plaintextChars.count; i += 2) { if (i + 1 >= plaintextChars.count) break; // 获取两个明文字母 NSString *char1 = [plaintextChars[i] stringValue]; NSString *char2 = [plaintextChars[i + 1] stringValue]; // 查找两个字符在密钥矩阵中的位置 int pos1 = [self getPosition:char1 inCipherTable]; int pos2 = [self getPosition:char2 inCipherTable]; // 如果两个字符的位置相同，自动生成一个随机的偏移量 if (pos1 == pos2) { // 偏移量可以是0到25之间的随机数 int offset = [self generateRandomOffset]; pos2 = (pos2 + offset) % 26; } // 加密 int keyChar1 = keyMatrix[pos1][0]; int keyChar2 = keyMatrix[pos2][0]; int encrypted1 = (pos1 + keyChar1) % 26; int encrypted2 = (pos2 + keyChar2) % 26; // 将加密后的结果转换为字符 NSString *encryptedChar1 = [NSString stringWithFormat:@"%c", (unichar)('A' + encrypted1)]; NSString *encryptedChar2 = [NSString stringWithFormat:@"%c", (unichar)('A' + encrypted2)]; [cipherText addObject:encryptedChar1]; [cipherText addObject:encryptedChar2]; } // 5. 转换为字符串 NSString *result = [[cipherText componentsJoined] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; return result;}- (int)getPosition:(NSString *)char inCipherTable:(NSMutableArray *)cipherTable { for (int i = 0; i < cipherTable.count; i++) { for (int j = 0; j < cipherTable[i].count; j++) { if ([cipherTable[i][j] isEqualToString:char]) { return [self getValue:i][j]; } } } return -1;}- (NSArray *)getValue:(int)row { return [NSArray arrayWithValues:matrix[row]];}- (void)fillKeyMatrix:(NSString *)key withMatrix:(NSMutableArray *)matrix { key = [key uppercaseString]; NSCharacterSet *invalidChars = [NSCharacterSet characterSetWithCharactersInString:@"^~`123-!@#$%&*()_+={}|;:'\"<>,.?"]; NSString * cleanedKey = [key stringByReplacingOccurrencesOfCharactersInString:invalidChars withString:@""]; cleanedKey = [cleanedKey substringToIndex:arc4random_uniform((int)cleanedKey.length - 2)]; for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { matrix[i][j] = [cleanedKey substringWithRange:NSMakeRange(i + j, 1)]; } }}- (void)generatePermutationMatrix:(NSMutableArray *)keyMatrix permutationMatrix:(NSMutableArray *)permMatrix { for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { NSString *keyChar = [keyMatrix[i][j] stringValue]; int keyIndex = [self getPosition:[keyChar] inCipherTable:permMatrix]; if (keyIndex != -1) { permMatrix[i][j] = [keyMatrix[keyIndex][0] stringValue]; } else { permMatrix[i][j] = @"A"; } } }}- (void)generateCipherTable:(NSMutableArray *)permMatrix cipherTable:(NSMutableArray *)cipherTable { for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { cipherTable[i][j] = [permMatrix[i][j] stringValue]; } }}- (int)generateRandomOffset { return (int)(arc4random() % 26);}@end
这个实现包括以下功能：
通过以上代码实现，您可以实现Playfair密码的加密功能。
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