给马克思主义者的加密通讯简史

据说中国古代打仗，事先约定一首诗，这首诗一共20个字，每个字代表什么意思，如撤退、进攻等，都事先说好。

将军发布命令的时候，就说一个字，如果传令兵被敌方截去了，敌方只能得到一个字的情报，最终还是不得要领。

这种思想，一直延续了很久，20年代上海的地下党仍然使用密码本。

当然，密码本几个月到几年就更换一次。这样显然会更安全。

外国的古人也不傻，据说凯撒大帝也发明了一种办法，这种办法被后人称之为“凯撒加密”。

众所周知，西方人使用字母文字，所以，凯撒就用一个字母代替后一个字母。

现在，你仍然可以使用这种非常经典的加密方式。比如你收到一封来自女神的信，上面写着：

N QTAJ Z

然后你敏锐的观察到N和I相差5个字母，Q和L也相差5个字母，然后你大胆猜测，上面的密文代表是

I LOVE U

验算一下，果然成立，所有的字母之间的距离都是5 。

这时候，你就可以醒过来了。

距离都是5，显然很容易被敌军猜到，你可以随便定义这个距离，甚至，你可以定义一个字母对应表。这样敌军就更难猜了。

但这并不代表大家猜不出来。

比如

crm ma kfa acdkdav ic k dfakw jipin mkf wauwicd meaweaf wekw ckwirc rf kcl ckwirc ur jrcjaipavkcv ur vavijkwav jkc nrcd acvxfa ma kfa gaw rc k dfakw bkwwnahianv rh wekw mkf ma ekpa jrga wr vavijkwa k zrfwirc rh wekw hianv ku k hickn fauwicd znkja hrf werua mer eafa dkpa weaif nipau wekw wekw ckwirc gidew nipa iw

这看起来是一团乱码，但是我们可以统计一下字母出现的频率。

k出现的频率很高。是一个单个字母的单词，所以k可能是I或者a。我用i试了，觉得不对劲，于是用a试试。

我直接把我的实验记录放在这里吧

xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k i
crm ma ifa acdidav ic i dfaiw jipin mif wauwicd meaweaf weiw ciwirc rf icl ciwirc ur jrcjaipavicv ur vavijiwav jic nrcd acvxfa ma ifa gaw rc i dfaiw biwwnahianv rh weiw mif ma eipa jrga wr vavijiwa i zrfwirc rh weiw hianv iu i hicin fauwicd znija hrf werua mer eafa dipa weaif nipau weiw weiw ciwirc gidew nipa iw 
iu inwrdaweaf hiwwicd icv zfrzaf weiw ma uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I
crm ma Ifa acdIdav ic I dfaIw jipin mIf wauwicd meaweaf weIw cIwirc rf Icl cIwirc ur jrcjaipavIcv ur vavijIwav jIc nrcd acvxfa ma Ifa gaw rc I dfaIw bIwwnahianv rh weIw mIf ma eIpa jrga wr vavijIwa I zrfwirc rh weIw hianv Iu I hicIn fauwicd znIja hrf werua mer eafa dIpa weaif nipau weIw weIw cIwirc gidew nipa iw 
iu Inwrdaweaf hiwwicd Icv zfrzaf weIw ma uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr ma OF
crO OF IfF FcdIdFv ic I dfFIw jipin OIf wFuwicd OeFweFf weIw cIwirc rf Icl cIwirc ur jrcjFipFvIcv ur vFvijIwFv jIc nrcd FcvxfF OF IfF gFw rc I dfFIw bIwwnFhiFnv rh weIw OIf OF eIpF jrgF wr vFvijIwF I zrfwirc rh weIw hiFnv Iu I hicIn fFuwicd znIjF hrf weruF Oer eFfF dIpF weFif nipFu weIw weIw cIwirc gidew nipF iw 
iu InwrdFweFf hiwwicd Icv zfrzFf weIw OF uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr rc OF
FOm ma Ifa aFdIdav iF I dfaIw jipin mIf wauwiFd meaweaf weIw FIwiOF Of IFl FIwiOF uO jOFjaipavIFv uO vavijIwav jIF nOFd aFvxfa ma Ifa gaw OF I dfaIw bIwwnahianv Oh weIw mIf ma eIpa jOga wO vavijIwa I zOfwiOF Oh weIw hianv Iu I hiFIn fauwiFd znIja hOf weOua meO eafa dIpa weaif nipau weIw weIw FIwiOF gidew nipa iw 
iu InwOdaweaf hiwwiFd IFv zfOzaf weIw ma ueOxnv vO weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I 
crm ma Ifa acdIdav ic I dfaIw jipin mIf wauwicd meaweaf weIw cIwirc rf Icl cIwirc ur jrcjaipavIcv ur vavijIwav jIc nrcd acvxfa ma Ifa gaw rc I dfaIw bIwwnahianv rh weIw mIf ma eIpa jrga wr vavijIwa I zrfwirc rh weIw hianv Iu I hicIn fauwicd znIja hrf werua mer eafa dIpa weaif nipau weIw weIw cIwirc gidew nipa iw 
iu Inwrdaweaf hiwwicd Icv zfrzaf weIw ma uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr rc OF
FOm ma Ifa aFdIdav iF I dfaIw jipin mIf wauwiFd meaweaf weIw FIwiOF Of IFl FIwiOF uO jOFjaipavIFv uO vavijIwav jIF nOFd aFvxfa ma Ifa gaw OF I dfaIw bIwwnahianv Oh weIw mIf ma eIpa jOga wO vavijIwa I zOfwiOF Oh weIw hianv Iu I hiFIn fauwiFd znIja hOf weOua meO eafa dIpa weaif nipau weIw weIw FIwiOF gidew nipa iw 
iu InwOdaweaf hiwwiFd IFv zfOzaf weIw ma ueOxnv vO weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr rc OF | tr m R
FOR Ra Ifa aFdIdav iF I dfaIw jipin RIf wauwiFd Reaweaf weIw FIwiOF Of IFl FIwiOF uO jOFjaipavIFv uO vavijIwav jIF nOFd aFvxfa Ra Ifa gaw OF I dfaIw bIwwnahianv Oh weIw RIf Ra eIpa jOga wO vavijIwa I zOfwiOF Oh weIw hianv Iu I hiFIn fauwiFd znIja hOf weOua ReO eafa dIpa weaif nipau weIw weIw FIwiOF gidew nipa iw 
iu InwOdaweaf hiwwiFd IFv zfOzaf weIw Ra ueOxnv vO weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I 
crm ma Ifa acdIdav ic I dfaIw jipin mIf wauwicd meaweaf weIw cIwirc rf Icl cIwirc ur jrcjaipavIcv ur vavijIwav jIc nrcd acvxfa ma Ifa gaw rc I dfaIw bIwwnahianv rh weIw mIf ma eIpa jrga wr vavijIwa I zrfwirc rh weIw hianv Iu I hicIn fauwicd znIja hrf werua mer eafa dIpa weaif nipau weIw weIw cIwirc gidew nipa iw 
iu Inwrdaweaf hiwwicd Icv zfrzaf weIw ma uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr ma IN
crI IN IfN NcdIdNv ic I dfNIw jipin IIf wNuwicd IeNweNf weIw cIwirc rf Icl cIwirc ur jrcjNipNvIcv ur vNvijIwNv jIc nrcd NcvxfN IN IfN gNw rc I dfNIw bIwwnNhiNnv rh weIw IIf IN eIpN jrgN wr vNvijIwN I zrfwirc rh weIw hiNnv Iu I hicIn fNuwicd znIjN hrf weruN Ier eNfN dIpN weNif nipNu weIw weIw cIwirc gidew nipN iw 
iu InwrdNweNf hiwwicd Icv zfrzNf weIw IN uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr ma AN
crA AN IfN NcdIdNv ic I dfNIw jipin AIf wNuwicd AeNweNf weIw cIwirc rf Icl cIwirc ur jrcjNipNvIcv ur vNvijIwNv jIc nrcd NcvxfN AN IfN gNw rc I dfNIw bIwwnNhiNnv rh weIw AIf AN eIpN jrgN wr vNvijIwN I zrfwirc rh weIw hiNnv Iu I hicIn fNuwicd znIjN hrf weruN Aer eNfN dIpN weNif nipNu weIw weIw cIwirc gidew nipN iw 
iu InwrdNweNf hiwwicd Icv zfrzNf weIw AN uerxnv vr weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr i A
crm ma Ifa acdIdav Ac I dfaIw jApAn mIf wauwAcd meaweaf weIw cIwArc rf Icl cIwArc ur jrcjaApavIcv ur vavAjIwav jIc nrcd acvxfa ma Ifa gaw rc I dfaIw bIwwnahAanv rh weIw mIf ma eIpa jrga wr vavAjIwa I zrfwArc rh weIw hAanv Iu I hAcIn fauwAcd znIja hrf werua mer eafa dIpa weaAf nApau weIw weIw cIwArc gAdew nApa Aw 
Au Inwrdaweaf hAwwAcd Icv zfrzaf weIw ma uerxnv vr weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr i A | tr c N
Nrm ma Ifa aNdIdav AN I dfaIw jApAn mIf wauwANd meaweaf weIw NIwArN rf INl NIwArN ur jrNjaApavINv ur vavAjIwav jIN nrNd aNvxfa ma Ifa gaw rN I dfaIw bIwwnahAanv rh weIw mIf ma eIpa jrga wr vavAjIwa I zrfwArN rh weIw hAanv Iu I hANIn fauwANd znIja hrf werua mer eafa dIpa weaAf nApau weIw weIw NIwArN gAdew nApa Aw 
Au Inwrdaweaf hAwwANd INv zfrzaf weIw ma uerxnv vr weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr i A | tr c N | tr rm OW
NOW Wa Ifa aNdIdav AN I dfaIw jApAn WIf wauwANd Weaweaf weIw NIwAON Of INl NIwAON uO jONjaApavINv uO vavAjIwav jIN nONd aNvxfa Wa Ifa gaw ON I dfaIw bIwwnahAanv Oh weIw WIf Wa eIpa jOga wO vavAjIwa I zOfwAON Oh weIw hAanv Iu I hANIn fauwANd znIja hOf weOua WeO eafa dIpa weaAf nApau weIw weIw NIwAON gAdew nApa Aw 
Au InwOdaweaf hAwwANd INv zfOzaf weIw Wa ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr i A | tr c N | tr rm OW | tr a E
NOW WE IfE ENdIdEv AN I dfEIw jApAn WIf wEuwANd WeEweEf weIw NIwAON Of INl NIwAON uO jONjEApEvINv uO vEvAjIwEv jIN nONd ENvxfE WE IfE gEw ON I dfEIw bIwwnEhAEnv Oh weIw WIf WE eIpE jOgE wO vEvAjIwE I zOfwAON Oh weIw hAEnv Iu I hANIn fEuwANd znIjE hOf weOuE WeO eEfE dIpE weEAf nApEu weIw weIw NIwAON gAdew nApE Aw 
Au InwOdEweEf hAwwANd INv zfOzEf weIw WE ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr i A | tr c N | tr rm OW | tr a E | tr h F
NOW WE IfE ENdIdEv AN I dfEIw jApAn WIf wEuwANd WeEweEf weIw NIwAON Of INl NIwAON uO jONjEApEvINv uO vEvAjIwEv jIN nONd ENvxfE WE IfE gEw ON I dfEIw bIwwnEFAEnv OF weIw WIf WE eIpE jOgE wO vEvAjIwE I zOfwAON OF weIw FAEnv Iu I FANIn fEuwANd znIjE FOf weOuE WeO eEfE dIpE weEAf nApEu weIw weIw NIwAON gAdew nApE Aw 
Au InwOdEweEf FAwwANd INv zfOzEf weIw WE ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr k I | tr i A | tr c N | tr rm OW | tr a E | tr h F | tr f R
NOW WE IRE ENdIdEv AN I dREIw jApAn WIR wEuwANd WeEweER weIw NIwAON OR INl NIwAON uO jONjEApEvINv uO vEvAjIwEv jIN nONd ENvxRE WE IRE gEw ON I dREIw bIwwnEFAEnv OF weIw WIR WE eIpE jOgE wO vEvAjIwE I zORwAON OF weIw FAEnv Iu I FANIn REuwANd znIjE FOR weOuE WeO eERE dIpE weEAR nApEu weIw weIw NIwAON gAdew nApE Aw 
Au InwOdEweER FAwwANd INv zROzER weIw WE ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a I | tr i A | tr c N | tr rm OW | tr a E | tr h F | tr f R
NOW WI kRI INdkdIv AN k dRIkw jApAn WkR wIuwANd WeIweIR wekw NkwAON OR kNl NkwAON uO jONjIApIvkNv uO vIvAjkwIv jkN nONd INvxRI WI kRI gIw ON k dRIkw bkwwnIFAInv OF wekw WkR WI ekpI jOgI wO vIvAjkwI k zORwAON OF wekw FAInv ku k FANkn RIuwANd znkjI FOR weOuI WeO eIRI dkpI weIAR nApIu wekw wekw NkwAON gAdew nApI Aw 
Au knwOdIweIR FAwwANd kNv zROzIR wekw WI ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr i A | tr c N | tr rm OW | tr a E | tr h F | tr f R
NOW WE kRE ENdkdEv AN k dREkw jApAn WkR wEuwANd WeEweER wekw NkwAON OR kNl NkwAON uO jONjEApEvkNv uO vEvAjkwEv jkN nONd ENvxRE WE kRE gEw ON k dREkw bkwwnEFAEnv OF wekw WkR WE ekpE jOgE wO vEvAjkwE k zORwAON OF wekw FAEnv ku k FANkn REuwANd znkjE FOR weOuE WeO eERE dkpE weEAR nApEu wekw wekw NkwAON gAdew nApE Aw 
Au knwOdEweER FAwwANd kNv zROzER wekw WE ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr i A | tr c N | tr rm OW | tr h F | tr f R
NOW WE kRE ENdkdEv AN k dREkw jApAn WkR wEuwANd WeEweER wekw NkwAON OR kNl NkwAON uO jONjEApEvkNv uO vEvAjkwEv jkN nONd ENvxRE WE kRE gEw ON k dREkw bkwwnEFAEnv OF wekw WkR WE ekpE jOgE wO vEvAjkwE k zORwAON OF wekw FAEnv ku k FANkn REuwANd znkjE FOR weOuE WeO eERE dkpE weEAR nApEu wekw wekw NkwAON gAdew nApE Aw 
Au knwOdEweER FAwwANd kNv zROzER wekw WE ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr i A | tr c N | tr rm OW | tr h F | tr f R | tr k A
NOW WE ARE ENdAdEv AN A dREAw jApAn WAR wEuwANd WeEweER weAw NAwAON OR ANl NAwAON uO jONjEApEvANv uO vEvAjAwEv jAN nONd ENvxRE WE ARE gEw ON A dREAw bAwwnEFAEnv OF weAw WAR WE eApE jOgE wO vEvAjAwE A zORwAON OF weAw FAEnv Au A FANAn REuwANd znAjE FOR weOuE WeO eERE dApE weEAR nApEu weAw weAw NAwAON gAdew nApE Aw 
Au AnwOdEweER FAwwANd ANv zROzER weAw WE ueOxnv vO weAu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A
NOW WE ARE ENdAdEv iN A dREAw jipin WAR wEuwiNd WeEweER weAw NAwiON OR ANl NAwiON uO jONjEipEvANv uO vEvijAwEv jAN nONd ENvxRE WE ARE gEw ON A dREAw bAwwnEFiEnv OF weAw WAR WE eApE jOgE wO vEvijAwE A zORwiON OF weAw FiEnv Au A FiNAn REuwiNd znAjE FOR weOuE WeO eERE dApE weEiR nipEu weAw weAw NAwiON gidew nipE iw 
iu AnwOdEweER FiwwiNd ANv zROzER weAw WE ueOxnv vO weiu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I
NOW WE ARE ENdAdEv IN A dREAw jIpIn WAR wEuwINd WeEweER weAw NAwION OR ANl NAwION uO jONjEIpEvANv uO vEvIjAwEv jAN nONd ENvxRE WE ARE gEw ON A dREAw bAwwnEFIEnv OF weAw WAR WE eApE jOgE wO vEvIjAwE A zORwION OF weAw FIEnv Au A FINAn REuwINd znAjE FOR weOuE WeO eERE dApE weEIR nIpEu weAw weAw NAwION gIdew nIpE Iw 
Iu AnwOdEweER FIwwINd ANv zROzER weAw WE ueOxnv vO weIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H
NOW WE ARE ENdAdEv IN A dREAw jIpIn WAR wEuwINd WHEwHER wHAw NAwION OR ANl NAwION uO jONjEIpEvANv uO vEvIjAwEv jAN nONd ENvxRE WE ARE gEw ON A dREAw bAwwnEFIEnv OF wHAw WAR WE HApE jOgE wO vEvIjAwE A zORwION OF wHAw FIEnv Au A FINAn REuwINd znAjE FOR wHOuE WHO HERE dApE wHEIR nIpEu wHAw wHAw NAwION gIdHw nIpE Iw 
Iu AnwOdEwHER FIwwINd ANv zROzER wHAw WE uHOxnv vO wHIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D
NOW WE ARE ENdAdED IN A dREAw jIpIn WAR wEuwINd WHEwHER wHAw NAwION OR ANl NAwION uO jONjEIpEDAND uO DEDIjAwED jAN nONd ENDxRE WE ARE gEw ON A dREAw bAwwnEFIEnD OF wHAw WAR WE HApE jOgE wO DEDIjAwE A zORwION OF wHAw FIEnD Au A FINAn REuwINd znAjE FOR wHOuE WHO HERE dApE wHEIR nIpEu wHAw wHAw NAwION gIdHw nIpE Iw 
Iu AnwOdEwHER FIwwINd AND zROzER wHAw WE uHOxnD DO wHIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT
NOW WE ARE ENdAdED IN A dREAT CIpIn WAR TEuTINd WHETHER THAT NATION OR ANl NATION uO CONCEIpEDAND uO DEDICATED CAN nONd ENDxRE WE ARE gET ON A dREAT bATTnEFIEnD OF THAT WAR WE HApE COgE TO DEDICATE A zORTION OF THAT FIEnD Au A FINAn REuTINd znACE FOR THOuE WHO HERE dApE THEIR nIpEu THAT THAT NATION gIdHT nIpE IT 
Iu AnTOdETHER FITTINd AND zROzER THAT WE uHOxnD DO THIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT |tr d G
NOW WE ARE ENGAGED IN A GREAT CIpIn WAR TEuTING WHETHER THAT NATION OR ANl NATION uO CONCEIpEDAND uO DEDICATED CAN nONG ENDxRE WE ARE gET ON A GREAT bATTnEFIEnD OF THAT WAR WE HApE COgE TO DEDICATE A zORTION OF THAT FIEnD Au A FINAn REuTING znACE FOR THOuE WHO HERE GApE THEIR nIpEu THAT THAT NATION gIGHT nIpE IT 
Iu AnTOGETHER FITTING AND zROzER THAT WE uHOxnD DO THIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT |tr d G | tr pn VL
NOW WE ARE ENGAGED IN A GREAT CIVIL WAR TEuTING WHETHER THAT NATION OR ANl NATION uO CONCEIVEDAND uO DEDICATED CAN LONG ENDxRE WE ARE gET ON A GREAT bATTLEFIELD OF THAT WAR WE HAVE COgE TO DEDICATE A zORTION OF THAT FIELD Au A FINAL REuTING zLACE FOR THOuE WHO HERE GAVE THEIR LIVEu THAT THAT NATION gIGHT LIVE IT 
Iu ALTOGETHER FITTING AND zROzER THAT WE uHOxLD DO THIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT |tr d G | tr pn VL | tr g M
NOW WE ARE ENGAGED IN A GREAT CIVIL WAR TEuTING WHETHER THAT NATION OR ANl NATION uO CONCEIVEDAND uO DEDICATED CAN LONG ENDxRE WE ARE MET ON A GREAT bATTLEFIELD OF THAT WAR WE HAVE COME TO DEDICATE A zORTION OF THAT FIELD Au A FINAL REuTING zLACE FOR THOuE WHO HERE GAVE THEIR LIVEu THAT THAT NATION MIGHT LIVE IT 
Iu ALTOGETHER FITTING AND zROzER THAT WE uHOxLD DO THIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT |tr d G | tr pn VL | tr g M | tr z P
NOW WE ARE ENGAGED IN A GREAT CIVIL WAR TEuTING WHETHER THAT NATION OR ANl NATION uO CONCEIVEDAND uO DEDICATED CAN LONG ENDxRE WE ARE MET ON A GREAT bATTLEFIELD OF THAT WAR WE HAVE COME TO DEDICATE A PORTION OF THAT FIELD Au A FINAL REuTING PLACE FOR THOuE WHO HERE GAVE THEIR LIVEu THAT THAT NATION MIGHT LIVE IT 
Iu ALTOGETHER FITTING AND PROPER THAT WE uHOxLD DO THIu
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT |tr d G | tr pn VL | tr g M | tr z P | tr u S
NOW WE ARE ENGAGED IN A GREAT CIVIL WAR TESTING WHETHER THAT NATION OR ANl NATION SO CONCEIVEDAND SO DEDICATED CAN LONG ENDxRE WE ARE MET ON A GREAT bATTLEFIELD OF THAT WAR WE HAVE COME TO DEDICATE A PORTION OF THAT FIELD AS A FINAL RESTING PLACE FOR THOSE WHO HERE GAVE THEIR LIVES THAT THAT NATION MIGHT LIVE IT 
IS ALTOGETHER FITTING AND PROPER THAT WE SHOxLD DO THIS
xiaochi@ZPX5YU6G2Z22SV2:/mnt/e/picasso250/az$ cat enc.txt | tr a E | tr c N | tr rm OW | tr h F | tr f R | tr k A | tr i I | tr e H | tr v D | tr jw CT |tr d G | tr pn VL | tr g M | tr z P | tr u S | tr x U
NOW WE ARE ENGAGED IN A GREAT CIVIL WAR TESTING WHETHER THAT NATION OR ANl NATION SO CONCEIVEDAND SO DEDICATED CAN LONG ENDURE WE ARE MET ON A GREAT bATTLEFIELD OF THAT WAR WE HAVE COME TO DEDICATE A PORTION OF THAT FIELD AS A FINAL RESTING PLACE FOR THOSE WHO HERE GAVE THEIR LIVES THAT THAT NATION MIGHT LIVE IT 
IS ALTOGETHER FITTING AND PROPER THAT WE SHOULD DO THIS

有耐心的同学可以看看，经过前面几次不靠谱的实验，我很快就解密出来了。

这种套路叫做频率分析。为了降低难度，我使用的是分好词的密文，实际上，不分词最终也可以解密，而且你截获的密文越多，解密的可能性就越高。

为了防止敌人猜出来，我们的密码表就要常换常新。

这种加密思路一直延续到二战时期。

德军发明了一种叫做“英尼格玛”的机器，他能根据电路接线的不同，生成不同的字母对应表。

这种密码技术在当时非常先进，给盟军造成了很大的麻烦，幸亏图灵等人出手破解了这种密码。

关于这个破解还有个细节。据说最初德军的数学家把机器原型交付给军方的时候，军方问了一个很“聪明”的问题，就是e字母会不会对应到e字母自身。数学家很老实的回答，是有可能的。

军方立刻觉得数学家很蠢，要求更改程序，使得一个字母永远不会加密成自身。

数学家照做了。

结果战争时期，英军截获了一条密文。里面什么字母都有，就是没有e。

那么英国的数学家们立刻判断，这条密文的原文全是e。

他们的判断是准确的。这条新推测出的情报，加速了密码机制的破解。

战后调查表明，那天的一个加密员想要测试机器，就顺手在机器上摁了十几个e发送了出去。

希望德国的将军们以后不要再犯这种小聪明。

在破解“英尼格玛”的过程中，产生了一个副产品：计算机。

所以后来我们就开始用计算机加密。自然，可以使用一些计算量非常大的加密方式。

这样，使得纯人力破解加密不再可行。

我刚才讲的几种古典加密方式，都属于对称加密。什么叫对称加密呢？就是通讯双方持有一份相同的密码本（或者专业点，叫密钥）。

而最新科技又使得我们可以使用另一种加密方式，是的，你猜出来了，叫做 非对称加密。

非对称加密利用了一类数学问题，这类数学问题正着算很简单，但是倒着算很难。

分解质因数就是其中一种。

举个简单的例子，计算3x7很简单，但是分解21使得他是两个质数的乘积就很困难。

当然，这个例子太简单了。我另一个例子：100001087x100000841这个很简单

但是10000147399909553是哪两个质数的的乘积呢？这就比较困难。不论对人类，还是对计算机。

那么我们就可以先计算好两个大质数，然后乘起来。这个乘积结果数字可以公开告知所有人，这就是公钥，是公开的。而那两个具体的大质数，就是私钥，需要自己小心保存。

这样，我们就可以让人用公钥加密，然后我们再用私钥解密。

形象一点的说法，就是你有一把钥匙，然后你造了很多锁，给所有人，所有人都可以给你寄来小箱子，但这些小箱子只有你能打开。

当然，如果你要具体的和某个人通讯，你还要检查一下，这个小箱子是不是真的由这个人打造的。在古代可能要放一个贴身的玉佩什么的。现代只需要数字签名一下，就可以了。

数字签名的原理依然依赖于之前所讲到公钥私钥体系。发送方用自己的私钥签名，而接收方用发送方的公钥验证签名。因为私钥公钥的 数学关系，保证了接收方可以确保直到这是由发送方的私钥运算得出的结果，但同时不用知道具体的私钥。

在破解“英尼格玛”的过程中，盟军缴获了一台机器，也加速了密码破译过程。

密码学家们痛定思痛，决定不再把加密过程视为秘密。加密过程应该是公开的，可供查阅的。但是密钥是保密的。

现代的加密方式，包括AES家族，RSA家族等，都是遵循这一策略的，算法都是公开的。

马克思主义者不会缺少实践环节。

第一个实践是对称加密。

这次实践用到的工具是openssl，加密方式是-aes-256-cbc（美国军方也使用此加密标准，或许此加密方式有美国军方安装的后门，或许没有）

加密：

openssl enc -aes-256-cbc -a -in file.txt -out file.txt.1 -k xiaochi -iter 100000

解密

openssl enc -aes-256-cbc -d -a -in file.txt.1 -out file.txt.out -k xiaochi -iter 100000

第二个实践是非对称加密

所用到的工具是opengpg（开源，或许开源社区的天才会在其中加入后门，或许不会）

以下教程包含了加解密和验证签名。

OpenGPG尝试