仿射密码的硬破解

硬破解仿射密码

目录

仿射密码加解密公式

需要破解的原文

Ptfxgj Jnno-afv wn Htzaixojv Tjtxg
Af Yd Mqxzn
Kvif bdxvwsf X wtlv zf svtkv
Tp bdxvwsf tp X htzv qviv;
Bdxvwsf X rtkv jnno-afv
Wn wqv inpf hsndop xg wqv rvpwvig plf.
Wqv jnsovg rxssnrp af wqv ixkvipxov
Tiv fndgj aixovp xg wqv pvwwxgj pdg;
Wqvxi ivcsvhwxngp ng wqv pqxzzvixgj rtkvp
Tsrtfp sxgjvi xg wqv ovuwq nc zf qvtiw.
Wqv csntwxgj qvtiw jinrxgj xg wqv psdojv
Prtfp svxpdivsf dgovi wqv rtwvi;
Xg wqv jvgwsv rtkvp nc Htzaixojv
X rndso av t rtwvi ustgw!
Wqtw unns dgovi wqv pqtov nc vsz wivvp
Qnsop gnw rtwvi adw wqv itxganr cinz wqv plf;
Pqtwwvivo wn uxvhvp tzngj wqv odhlrvvop
Xp wqv pvoxzvgw nc t itxganr-sxlv oivtz.
Wn pvvl t oivtz? Edpw wn unsv t antw dupwivtz
Wn rqviv wqv jivvg jitpp xp zniv kviotgw;
Ni wn qtkv wqv antw cdssf sntovo rxwq pwtisxjqw
Tgo pxgj tsndo xg wqv pusvgoni nc pwtisxjqw.
Adw X htggnw pxgj tsndo
Bdxvwgvpp xp zf ctivrvss zdpxh;
Vkvg pdzzvi xgpvhwp qvtu pxsvghv cni zv
Pxsvgw xp Htzaixojv wngxjqw!
Kvif bdxvwsf X wtlv zf svtkv
Tp bdxvwsf tp X htzv qviv;
Jvgwsf X csxhl zf psvvkvp
Gnw vkvg t rxpu nc hsndo rxss X aixgj trtf

破解的算法分析

1. 第一步：由仿射加密可知k必须与26互素；
2. 第二步：k_1与k互为逆元，b可取任意值；
3. 第三步：取不同的k和b进行遍历输出结果，观察出能够读懂的语句，则此语句对应的k和b就是正确的k和b；
4. 第四步：使用网站输入对应的k和b，破解整篇文章的内容仿射加密网站。

C语言代码

C语言代码：
#include 
#include 
#include 

#define N 26

//判断是否互素
int isPrimeNum(int a)
{
    int i=2;
    for(;i<=a;i++)
    {
        if(0==a%i && 0==N%i)
        {
            return 0;
        }
    }
    return 1;
}
//获取a的逆元
int geta_(int a)
{
    int i=0;
    do{
        i++;

    }while(1!=a*i%N);
    return i;
}
//解密算法
char *decode(char *p_str,int _a,int b,int n)
{
    char c_str[40]="";
    int j=0;
    int i;
    while('\0'!=*p_str)
    {
        if(*p_str>='A' && *p_str<='Z')
        {
            i=*p_str-'A';
            i=((i-b+n)*_a)%n;
            c_str[j]=i+'A';
        }
        else if(*p_str>='a' && *p_str<='z')
        {
            i=*p_str-'a';
            i=((i-b+n)*_a)%n;
            c_str[j]=i+'a';
        }
        else
        {
            c_str[j]=*p_str;
        }

        p_str++;
        j++;
    }
    return &c_str[0];
}
int main()
{
    int a=1,b=1,a_;
    char p_str[40]="Ptfxgj Jnno-afv wn Htzaixojv Tjtxg";
    char c_str[40]="";
    for(;a<=25;a+=2)
    {
        if(0==isPrimeNum(a)){
            continue;
        }
        else{
            a_=geta_(a);
        }
        for(b=-10;b<=10;b++)
        {
            strcpy(c_str,decode(p_str,a_,b,N));
            printf("%d %d",a,b);
            printf("\t%s\n",c_str);
        }
    }
    return 0;
}

python代码

##判断是否与26互素
def isPN(a):
    for num in range(2,a):
        if 0==a%num and 0==26%num:
            return False
    return True

##求得逆元a_
def get_a_(a):
    i=1
    while (1!=(i*a)%26):
        i=i+1
    return i


##解密函数
def decodeMstr(mStr,a_,b):
    yStr=""
    for Char in mStr:
        if Char>='A' and Char<='Z':
            Int=ord(Char)-ord('A')
            Int=((Int-b+26)*a_)%26
            yStr=yStr+chr(Int+ord('A'))
        elif Char>='a' and Char<='z':
            Int=ord(Char)-ord('a')
            Int=((Int-b+26)*a_)%26
            yStr=yStr+chr(Int+ord('a'))
        else:
            yStr=yStr+Char
    return yStr

mStr="Ptfxgj Jnno-afv wn Htzaixojv Tjtxg"
for a in range(1,25,2):
    if False==isPN(a):
        continue
    else:
        a_=get_a_(a)
    for b in range(-10,10):
        yStr=decodeMstr(mStr,a_,b)
        print(yStr,end="\t")
        print(a,b)

效果展示

原文

Saying Good-bye to Cambridge Again
By Xu Zhimo
Very quietly I take my leave
As quietly as I came here;
Quietly I wave good-bye
To the rosy clouds in the western sky.
The golden willows by the riverside
Are young brides in the setting sun;
Their reflections on the shimmering waves
Always linger in the depth of my heart.
The floating heart growing in the sludge
Sways leisurely under the water;
In the gentle waves of Cambridge
I would be a water plant!
That pool under the shade of elm trees
Holds not water but the rainbow from the sky;
Shattered to pieces among the duckweeds
Is the sediment of a rainbow-like dream.
To seek a dream? Just to pole a boat upstream
To where the green grass is more verdant;
Or to have the boat fully loaded with starlight
And sing aloud in the splendor of starlight.
But I cannot sing aloud
Quietness is my farewell music;
Even summer insects heap silence for me
Silent is Cambridge tonight!
Very quietly I take my leave
As quietly as I came here;
Gently I flick my sleeves
Not even a wisp of cloud will I bring away