Hill Cipher

#include<stdio.h>

int main()
{
    unsigned int a[3][3] = {{6,24,1}, {13,16,10}, {20,17,15} };
    unsigned int b[3][3] = {{8,5,10}, {21,8,21}, {21,12,8} };

    int i, j, t = 0;

    unsigned int c[20], d[20];

    char msg[20];

    printf("Enter the Plain Text : ");
    scanf("%s", &msg);

    for(i=0; i<strlen(msg); i++)
    {
        c[i] = msg[i]-65;
        printf("%d", c[i]);
    }

    for(i=0; i<3; i++)
    {
        t = 0;
        for(j=0; j<3; j++)
        {
            t = t+(a[i][j]*c[j]);
        }
        d[i] = t%26;
    }

    printf("\nCipher Text : ");
    for(i=0; i<3; i++)
    {
        printf("%c", d[i]+65);
    }

    for(i=0; i<3; i++)
    {
        t = 0;
        for(j=0; j<3;j++)
        {
            t = t+(b[i][j]*d[j]);
        }
        c[i] = t%26;
    }

    printf("\nPlain Text : ");
    for(i=0; i<3; i++)
    {
        printf("%c", c[i]+65);
    }
}