picoCTF2020-Crypto

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picoCTF

Cryptography

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The Numbers

The Numbers

The flag is in the format PICOCTF{}

得到一串数字

16 9 3 15 3 20 6 { 20 8 5 14 21 13 2 5 18 19 13 1 19 15 14 }

根据hint，对照ASCII，已知部门为

80 73 67 79 67 84 70 { }

编写脚本，思路为after=before+64，或者手动加工也可得到flag.

caesar

caesar

caesar cipher tutorial

在线网站或者脚本都可解密，遍历后选取相对有意思的字符即是flag.

Easy1

Easy1

The one time pad can be cryptographically secure, but not when you know the key. Can you solve this? We’ve given you the encrypted flag, key, and a table to help UFJKXQZQUNB with the key of SOLVECRYPTO. Can you use this table to solve it?.

Submit your answer in our flag format. For example, if your answer was ‘hello’, you would submit ‘picoCTF{HELLO}’ as the flag.Please use all caps for the message.

据题意，已知该加密方式拥有明文和密钥，结合给出的字典，确定为维吉尼亚编码，在线网站或脚本都可解密得flag。

13

[13](Cryptography can be easy, do you know what ROT13 is? cvpbPGS{abg_gbb_onq_bs_n_ceboyrz})

This can be solved online if you don’t want to do it by hand!

题目描述可知加密方式为ROT13,在线网站或脚本即可解密。

la cifra de

[la cifra de](I found this cipher in an old book. Can you figure out what it says? Connect with nc jupiter.challenges.picoctf.org 50523)

There are tools that make this easy.Perhaps looking at history will help

Encrypted message:
Ne iy nytkwpsznyg nth it mtsztcy vjzprj zfzjy rkhpibj nrkitt ltc tnnygy ysee itd tte cxjltk

Ifrosr tnj noawde uk siyyzre, yse Bnretèwp Cousex mls hjpn xjtnbjytki xatd eisjd

Iz bls lfwskqj azycihzeej yz Brftsk ip Volpnèxj ls oy hay tcimnyarqj dkxnrogpd os 1553 my Mnzvgs Mazytszf Merqlsu ny hox moup Wa inqrg ipl. Ynr. Gotgat Gltzndtg Gplrfdo 

Ltc tnj tmvqpmkseaznzn uk ehox nivmpr g ylbrj ts ltcmki my yqtdosr tnj wocjc hgqq ol fy oxitngwj arusahje fuw ln guaaxjytrd catizm tzxbkw zf vqlckx hizm ceyupcz yz tnj fpvjc hgqqpohzCZK{m311a50_0x_a1rn3x3_h1ah3x6kp60egf}

Ehk ktryy herq-ooizxetypd jjdcxnatoty ol f aordllvmlbkytc inahkw socjgex, bls sfoe gwzuti 1467 my Rjzn Hfetoxea Gqmexyt.

Tnj Gimjyèrk Htpnjc iy ysexjqoxj dosjeisjd cgqwej yse Gqmexyt Doxn ox Fwbkwei Inahkw.

Tn 1508, Ptsatsps Zwttnjxiax tnbjytki ehk xz-cgqwej ylbaql rkhea (g rltxni ol xsilypd gqahggpty) ysaz bzuri wazjc bk f nroytcgq nosuznkse ol yse Bnretèwp Cousex.

Gplrfdo’y xpcuso butvlky lpvjlrki tn 1555 gx l cuseitzltoty ol yse lncsz. Yse rthex mllbjd ol yse gqahggpty fce tth snnqtki cemzwaxqj, bay ehk fwpnfmezx lnj yse osoed qptzjcs gwp mocpd hd xegsd ol f xnkrznoh vee usrgxp, wnnnh ify bk itfljcety hizm paim noxwpsvtydkse.

在线网站维吉尼亚解密可得flag.

词频分析搞了半天，555

rsa-pop-quiz

[rsa-pop-quiz](Class, take your seats! It’s PRIME-time for a quiz… nc jupiter.challenges.picoctf.org 41130)

RSA info

RSA层层解密：

# nc jupiter.challenges.picoctf.org 41130
Good morning class! It's me Ms. Adleman-Shamir-Rivest
Today we will be taking a pop quiz, so I hope you studied. Cramming just will not do!
You will need to tell me if each example is possible, given your extensive crypto knowledge.
Inputs and outputs are in decimal. No hex here!
#### NEW PROBLEM ####
q : 60413
p : 76753
##### PRODUCE THE FOLLOWING ####
n
IS THIS POSSIBLE and FEASIBLE? (Y/N):y
#### TIME TO SHOW ME WHAT YOU GOT! ###
n: 4636878989
Outstanding move!!!


#### NEW PROBLEM ####
p : 54269
n : 5051846941
##### PRODUCE THE FOLLOWING ####
q
IS THIS POSSIBLE and FEASIBLE? (Y/N):y
#### TIME TO SHOW ME WHAT YOU GOT! ###
q: 93089
Outstanding move!!!


#### NEW PROBLEM ####
e : 3
n : 12738162802910546503821920886905393316386362759567480839428456525224226445173031635306683726182522494910808518920409019414034814409330094245825749680913204566832337704700165993198897029795786969124232138869784626202501366135975223827287812326250577148625360887698930625504334325804587329905617936581116392784684334664204309771430814449606147221349888320403451637882447709796221706470239625292297988766493746209684880843111138170600039888112404411310974758532603998608057008811836384597579147244737606088756299939654265086899096359070667266167754944587948695842171915048619846282873769413489072243477764350071787327913
##### PRODUCE THE FOLLOWING ####
q
p
IS THIS POSSIBLE and FEASIBLE? (Y/N):n
Outstanding move!!!


#### NEW PROBLEM ####
q : 66347
p : 12611
##### PRODUCE THE FOLLOWING ####
totient(n)
IS THIS POSSIBLE and FEASIBLE? (Y/N):y
#### TIME TO SHOW ME WHAT YOU GOT! ###
totient(n): 836623060
Outstanding move!!!


#### NEW PROBLEM ####
plaintext : 6357294171489311547190987615544575133581967886499484091352661406414044440475205342882841236357665973431462491355089413710392273380203038793241564304774271529108729717
e : 3
n : 29129463609326322559521123136222078780585451208149138547799121083622333250646678767769126248182207478527881025116332742616201890576280859777513414460842754045651093593251726785499360828237897586278068419875517543013545369871704159718105354690802726645710699029936754265654381929650494383622583174075805797766685192325859982797796060391271817578087472948205626257717479858369754502615173773514087437504532994142632207906501079835037052797306690891600559321673928943158514646572885986881016569647357891598545880304236145548059520898133142087545369179876065657214225826997676844000054327141666320553082128424707948750331
##### PRODUCE THE FOLLOWING ####
ciphertext
IS THIS POSSIBLE and FEASIBLE? (Y/N):y
#### TIME TO SHOW ME WHAT YOU GOT! ###
ciphertext: 256931246631782714357241556582441991993437399854161372646318659020994329843524306570818293602492485385337029697819837182169818816821461486018802894936801257629375428544752970630870631166355711254848465862207765051226282541748174535990314552471546936536330397892907207943448897073772015986097770443616540466471245438117157152783246654401668267323136450122287983612851171545784168132230208726238881861407976917850248110805724300421712827401063963117423718797887144760360749619552577176382615108244813
Outstanding move!!!


#### NEW PROBLEM ####
ciphertext : 107524013451079348539944510756143604203925717262185033799328445011792760545528944993719783392542163428637172323512252624567111110666168664743115203791510985709942366609626436995887781674651272233566303814979677507101168587739375699009734588985482369702634499544891509228440194615376339573685285125730286623323
e : 3
n : 27566996291508213932419371385141522859343226560050921196294761870500846140132385080994630946107675330189606021165260590147068785820203600882092467797813519434652632126061353583124063944373336654246386074125394368479677295167494332556053947231141336142392086767742035970752738056297057898704112912616565299451359791548536846025854378347423520104947907334451056339439706623069503088916316369813499705073573777577169392401411708920615574908593784282546154486446779246790294398198854547069593987224578333683144886242572837465834139561122101527973799583927411936200068176539747586449939559180772690007261562703222558103359
##### PRODUCE THE FOLLOWING ####
plaintext
IS THIS POSSIBLE and FEASIBLE? (Y/N):n
Outstanding move!!!


#### NEW PROBLEM ####
q : 92092076805892533739724722602668675840671093008520241548191914215399824020372076186460768206814914423802230398410980218741906960527104568970225804374404612617736579286959865287226538692911376507934256844456333236362669879347073756238894784951597211105734179388300051579994253565459304743059533646753003894559
p : 97846775312392801037224396977012615848433199640105786119757047098757998273009741128821931277074555731813289423891389911801250326299324018557072727051765547115514791337578758859803890173153277252326496062476389498019821358465433398338364421624871010292162533041884897182597065662521825095949253625730631876637
e : 65537
##### PRODUCE THE FOLLOWING ####
d
IS THIS POSSIBLE and FEASIBLE? (Y/N):y
#### TIME TO SHOW ME WHAT YOU GOT! ###
d: 1405046269503207469140791548403639533127416416214210694972085079171787580463776820425965898174272870486015739516125786182821637006600742140682552321645503743280670839819078749092730110549881891271317396450158021688253989767145578723458252769465545504142139663476747479225923933192421405464414574786272963741656223941750084051228611576708609346787101088759062724389874160693008783334605903142528824559223515203978707969795087506678894006628296743079886244349469131831225757926844843554897638786146036869572653204735650843186722732736888918789379054050122205253165705085538743651258400390580971043144644984654914856729
Outstanding move!!!


#### NEW PROBLEM ####
p : 153143042272527868798412612417204434156935146874282990942386694020462861918068684561281763577034706600608387699148071015194725533394126069826857182428660427818277378724977554365910231524827258160904493774748749088477328204812171935987088715261127321911849092207070653272176072509933245978935455542420691737433
ciphertext : 18031488536864379496089550017272599246134435121343229164236671388038630752847645738968455413067773166115234039247540029174331743781203512108626594601293283737392240326020888417252388602914051828980913478927759934805755030493894728974208520271926698905550119698686762813722190657005740866343113838228101687566611695952746931293926696289378849403873881699852860519784750763227733530168282209363348322874740823803639617797763626570478847423136936562441423318948695084910283653593619962163665200322516949205854709192890808315604698217238383629613355109164122397545332736734824591444665706810731112586202816816647839648399
e : 65537
n : 23952937352643527451379227516428377705004894508566304313177880191662177061878993798938496818120987817049538365206671401938265663712351239785237507341311858383628932183083145614696585411921662992078376103990806989257289472590902167457302888198293135333083734504191910953238278860923153746261500759411620299864395158783509535039259714359526738924736952759753503357614939203434092075676169179112452620687731670534906069845965633455748606649062394293289967059348143206600765820021392608270528856238306849191113241355842396325210132358046616312901337987464473799040762271876389031455051640937681745409057246190498795697239
##### PRODUCE THE FOLLOWING ####
plaintext
IS THIS POSSIBLE and FEASIBLE? (Y/N):y
#### TIME TO SHOW ME WHAT YOU GOT! ###
plaintext: picoCTF{wA8_th4t$_ill3aGal..ode01e4bb}
That's not an int! Exiting

Tapping

[Tapping](Theres tapping coming in from the wires. What’s it saying nc jupiter.challenges.picoctf.org 28927.)

What kind of encoding uses dashes and dots?The flag is in the format PICOCTF{}

摩斯电码解密。

Mr-Worldwide

[Mr-Worldwide](A musician left us a message. What’s it mean?)

坐标，百度可查找经纬度，提取城市首字母得flag.

Flags

[Flags](What do the flags mean?)

The flag is in the format PICOCTF{}

简单的替换密码，百度找到对应网站和图片即可。https://en.wikipedia.org/wiki/International_maritime_signal_flags

waves over lambda

[waves over lambda](We made a lot of substitutions to encrypt this. Can you decrypt it? Connect with nc jupiter.challenges.picoctf.org 1981.)

Flag is not in the usual flag format

同为词频分析，观察后猜测jgsk=flag，丢进在线网站求解得flag.

miniRSA

miniRSA

RSA tutorial;How could having too small an e affect the security of this 2048 bit key?Make sure you don’t lose precision, the numbers are pretty big (besides the e value)

from Crypto.Util.number import *
import gmpy2

N=29331922499794985782735976045591164936683059380558950386560160105740343201513369939006307531165922708949619162698623675349030430859547825708994708321803705309459438099340427770580064400911431856656901982789948285309956111848686906152664473350940486507451771223435835260168971210087470894448460745593956840586530527915802541450092946574694809584880896601317519794442862977471129319781313161842056501715040555964011899589002863730868679527184420789010551475067862907739054966183120621407246398518098981106431219207697870293412176440482900183550467375190239898455201170831410460483829448603477361305838743852756938687673
e=3
c=2205316413931134031074603746928247799030155221252519872650080519263755075355825243327515211479747536697517688468095325517209911688684309894900992899707504087647575997847717180766377832435022794675332132906451858990782325436498952049751141 
m = int(gmpy2.iroot(c, e)[0])
print(long_to_bytes(m))
print(m)
#b'picoCTF{n33d_a_lArg3r_e_d0cd6eae}'
#13016382529449106065894479374027604750406953699090365388203722801043052339225981

b00tl3gRSA2

[b00tl3gRSA2](In RSA d is a lot bigger than e, why don’t we use d to encrypt instead of e? Connect with nc jupiter.challenges.picoctf.org 42900.)

What is e generally?

nc后发现e很大，维纳攻击脚本：

import  RSAwienerHacker
c=67725484828660171155495211630497256983804750771405173604915475315285337259554745019946599487641055680169265457644340938264529723371169972500050850583888499676593738216542714158045211992126456724042909731789545505279795504523037528761238149430515678580782074452909931229053012113137701929175885390372056497999
n=92908556262738254094065441172814586106067369443369499189214986491976931561738844273516700957530563178532708425726354645373760924007923816005398578319882528611540185427918571906094044173194388663365364134997826444445816336765012006409280712402476371185929572990909183399977560298360727962550970347800300222711
e=69520159460585947518483836148643582831918423640590763549444035011978832519891224565191960240113848478143117452571748866357688968863765140502139873387990270685914837356707507222866135679527601234329281217279226396840073020368275802208410100769859080342284164663788369069928003055037897805163984210272130270657
d =  RSAwienerHacker.hack_RSA(e,n)
if d:
    print(d)
#import hashlib
import binascii
#flag =hashlib.md5(hex(d)).hexdigest()
#print flag
m=pow(c,d,n)
print(hex(m))

十六进制转字符串后得明文。

john_pollard

[john_pollard](Sometimes RSA certificates are breakable)

The flag is in the format picoCTF{p,q};Try swapping p and q if it does not work