How to encrypt and decrypt the Caesar Cipher with python(Ⅱ)

上一篇文章中介绍了如何用python来解密凯撒密码,但是那是在已知密钥的情况下才可行的,大多数情况下我们是不知道加密所用的密钥,如果通过人力进行手工破解费时费力,而且极易可能出错,所以我们可以借助python来爆破。
How to encrypt and decrypt the Caesar Cipher with python(Ⅰ)

代码如下:

message = 'GUVF VF ZL FRPERG ZRFFNTR.'
LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

for key in range(len(LETTERS)):
    translated=''
    for symbol in message:
        if symbol in LETTERS:
            num=LETTERS.find(symbol)
            num-=key

            if num<0:
                num+=len(LETTERS)

            translated+=LETTERS[num]

        else:
            translated+=symbol
    print('Key #%s: %s' % (key, translated))

在这里我们没有设置key的值,而是通过遍历的方式让其取遍凯撒密码中所有可能的值。

Key #0: GUVF VF ZL FRPERG ZRFFNTR.
Key #1: FTUE UE YK EQODQF YQEEMSQ.
Key #2: ESTD TD XJ DPNCPE XPDDLRP.
Key #3: DRSC SC WI COMBOD WOCCKQO.
Key #4: CQRB RB VH BNLANC VNBBJPN.
Key #5: BPQA QA UG AMKZMB UMAAIOM.
Key #6: AOPZ PZ TF ZLJYLA TLZZHNL.
Key #7: ZNOY OY SE YKIXKZ SKYYGMK.
Key #8: YMNX NX RD XJHWJY RJXXFLJ.
Key #9: XLMW MW QC WIGVIX QIWWEKI.
Key #10: WKLV LV PB VHFUHW PHVVDJH.
Key #11: VJKU KU OA UGETGV OGUUCIG.
Key #12: UIJT JT NZ TFDSFU NFTTBHF.
Key #13: THIS IS MY SECRET MESSAGE.
Key #14: SGHR HR LX RDBQDS LDRRZFD.
Key #15: RFGQ GQ KW QCAPCR KCQQYEC.
Key #16: QEFP FP JV PBZOBQ JBPPXDB.
Key #17: PDEO EO IU OAYNAP IAOOWCA.
Key #18: OCDN DN HT NZXMZO HZNNVBZ.
Key #19: NBCM CM GS MYWLYN GYMMUAY.
Key #20: MABL BL FR LXVKXM FXLLTZX.
Key #21: LZAK AK EQ KWUJWL EWKKSYW.
Key #22: KYZJ ZJ DP JVTIVK DVJJRXV.
Key #23: JXYI YI CO IUSHUJ CUIIQWU.
Key #24: IWXH XH BN HTRGTI BTHHPVT.
Key #25: HVWG WG AM GSQFSH ASGGOUS.

爆破之后的结果如上。

很容易分析得到key=13时解密出的明文为正确的。

所以明文为

 THIS IS MY SECRET MESSAGE.

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