Playfair密码C语言源代码(共6页).doc

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1、精选优质文档-倾情为你奉上/PLAYFAIR.H头文件#ifndef _PLAY_FAIR_H_#define _PLAY_FAIR_H_void cst_playfair_table (char *in_key);void prnt_playfair_table ();int playfair_encrypt (char *plain_txt, char *cipher_txt);int playfair_decrypt (char *cipher_txt, char *plain_txt);#endif/PLAYFAIR.C源文件#include playfair.h#include #i

2、nclude #include char playfair_table55;void get_x_y (char c, int *x, int *y)int i, j;for (i = 0; i 5; +i)for (j = 0; j 5; +j)if (playfair_tableij = c)*x = i; *y = j;return;char get_char_x_y (int x, int y)if (x 0)x += 5;if (y 0)y += 5;return playfair_tablex % 5y % 5;void cst_playfair_table (char *in_k

3、ey)int i = 0, j, k;int char_count = 0, left_ch_index = 0;char ch, left_chs26 = 0, key26 = 0;int key_len;strcpy (key, in_key);key_len = strlen (key);while (1)if (keyi = )for (j = i; j key_len - 1; +j)keyj = keyj + 1;key_len-;if (i = key_len)break;i+;for (i = 0; i 1)for (k = j; k key_len -1; +k)keyk =

4、 keyk + 1;key_len-;elsej+;elsej+;if (j = key_len)break;if (char_count = 0)left_chsleft_ch_index+ = ch;for (i = 0; i left_ch_index; +i)keykey_len+ = left_chsi;for (i = 0; i 26; +i)if (keyi = z)for (j = i; j 25; +j)keyj = keyj + 1;for (i = 0; i 5; +i)for (j = 0; j 5; +j)playfair_tableij = key5 * i + j

5、;void prnt_playfair_table ()int i, j;printf (Playfair Table:n);for (i = 0; i 5; +i)printf (t);for (j = 0; j 5; +j)printf (%c , playfair_tableij);puts(n);int playfair_encrypt (char *plain_txt, char *cipher_txt)int length = strlen (plain_txt);int i = 0, j;int ax, ay, bx, by;char pch1, pch2, cch1, cch2

6、;int ch1_upper = 0, ch2_upper = 0;for (i = 0; i length; +i)if (plain_txti = z)plain_txti = x;if (length %2)plain_txtlength = x;length+;for (i = 0; i = A & pch1 = A & pch2 = Z)ch2_upper = 1;pch2 += 32;get_x_y (pch1, &ax, &ay);get_x_y (pch2, &bx, &by);if (ay = by)cch1 = get_char_x_y (ax + 1, ay);cch2

7、= get_char_x_y (bx + 1, by);else if (ax = bx)cch1 = get_char_x_y (ax, ay + 1);cch2 = get_char_x_y (bx, by + 1);elsecch1 = get_char_x_y (ax, by);cch2 = get_char_x_y (bx, ay);cipher_txti = cch1 - 32 * ch1_upper;cipher_txti + 1 = cch2 - 32 *ch2_upper;cipher_txtlength = 0;return length;int playfair_decr

8、ypt (char *cipher_txt, char *plain_txt)int length = strlen (plain_txt);int i = 0, j;int ax, ay, bx, by;char pch1, pch2, cch1, cch2;int ch1_upper = 0, ch2_upper = 0;for (i = 0; i = A & cch1 = A & cch2 = Z)ch2_upper = 1;cch2 += 32;get_x_y (cch1, &ax, &ay);get_x_y (cch2, &bx, &by);if (ay = by)pch1 = ge

9、t_char_x_y (ax - 1, ay);pch2 = get_char_x_y (bx - 1, by);else if (ax = bx)pch1 = get_char_x_y (ax, ay - 1);pch2 = get_char_x_y (bx, by - 1);elsepch1 = get_char_x_y (ax, by);pch2 = get_char_x_y (bx, ay);plain_txti = pch1 - 32 * ch1_upper;plain_txti + 1 = pch2 - 32 *ch2_upper;plain_txtlength = 0;retur

10、n length;/MAIN.C文件#include #include #include #include playfair.hint main ()char plain_txt1000, cipher_txt1000;char key26 = 0;printf (Please input your key (string): );scanf (%s, key);cst_playfair_table (key);printf (Keyword Table:n);prnt_playfair_table ();printf (Please input plain text: );scanf (%s, plain_txt);playfair_encrypt (plain_txt, cipher_txt);printf (Cipher is : %sn, cipher_txt);playfair_decrypt (cipher_txt, plain_txt);printf (After decryption, plain text is :%sn, plain_txt);return 0;专心-专注-专业