CS411-Homework 4 Solved

1.     Consider a deterministic RSA Oracle that is implemented at the server “cryptlygos.pythonanywhere.com/RSA_Oracle/<your_id”. When connected to the server, you will be sent a ciphertext                      and expected find out the corresponding plaintext   .  You can query the RSA Oracle with any ciphertext   , and you will be given the corresponding plaintext   . You can send as many queries as you want as long as   .

You can use the Python code RSA_Oracle_client.py to communicate with the server.

 

2.     Consider the RSA OAEP implemented at the server http://cryptlygos.pythonanywhere.com/RSA_OAEP/ <your_id. The server will send you a ciphertext (c), public key (e) and modulus (N). The RSA-OAEP implementation at the server is given in the file “RSA_OAEP.py”, in which the random number R is an 8-bit unsigned integer. 

 

I select a random four decimal digit PIN and encrypt it using RSA. You need to connect to the RSA encryption server that challenges you with   . Your mission is to find the randomly chosen PIN. You can use the Python code RSA_OAPE_client.py to communicate with the server.  

 

3.   Consider the ElGamal encryption algorithm implemented in the file “ElGamal.py”, which contains a flaw.  I used this implementation to encrypt a message using the following parameters:

 

q = 20229678282835322453606583744403220194075962461239010550087309021811

p = 12515043909394803753450411022649854273721537251011107748826811168459680628351391154487041320595006736239332192492236943966523053744476127728797963808151142506595330120621663371518281181204797831707349436558443139355672347825267728879376289677517268609959671235059224994785463608330669494457163250373581380036247652030969481046772013799271268710104487022164865004802864076066974153012125551060906054112920469869045223329577015935824864428612446723942040465300185917923305042033306319809712618872063796904132788285518497999327485929730921202745935936913834577610254298809205575162005025170878200786590751850006857921419

g = 2256483143741433163413007675067934542893022968337437312283381964942344365449719628255630752397325376452002398784394008507857025386943645437696558240874471345442532398588406749907930002481624160959132193798842426822193910104962138845873425590946341754334144292886002962901550160578482452138075339294826241799645761655320983735381974177635207208471824667516956679913974643342159550037320378814445802296879470561504511689460916200417902612323039671250567503846175990654512915878143201233050978046269551126178155060158781645062181955781969136435905570787457855530003987887049118699525033120811790739590564684316550493132

public key (h) =  1265126138933377994348793193477342224736956600354964713945582205290651827674605003741290400826146165752452701594226002213036650208863340321329798489264160728930653315907521926136642928347549825144026262035747350182493795559385070130959552499813885202334575993642935128132458545523498489490586883187848396314164874056757696154989511633927620869557222556876855999079308839417416012746206040455611002092520255736121673298963050693639916367968280807028975614596114022230524360150581344884219834519025619777858430431159461562871537004523472161672182851052258466610762884570310894027628303901161674783788320479747219000276

 

And the resulting ciphertext is

r = 3813677439444837990381281624769265484071989883494833765363155214071727573627590213038823018054653614040833306533736593789523636716088751609591517852868217052905415751457961942309213803782661174042131067555996860094296315483087375444362454092891960492098796234624392186112659124915872546640723139762874453050592110272036917039293020539724872406856066252779419482651672320132092421939867392668795959155312634804888215300607725584330531720210355201550529764936881761210810883102986464111409096572364185502722477587178710137175828696000683028806920671859797982157383943866111320227830105178421690303627627943337128795446 

 t= 10192033240113377640860169195054315981727514327329008790444130729107056930047299547755150775636237252367979032815426685448329207318153807026080454908281501010744250818034651670583477952735248499512182344163892706808295058861406156976805817052235913385764008189983049947270530103937035152142021836645533913141135755114076443812677194719578205394500861775715274421701692402012349095849491286883920257290062297268751154540379108778881866697419701006074165418163601856726590995982244188091368811214058385356303967475393274055097781937296940874619027724511050397080303621427005403200736696096764013637291006737753794119814

 

Can you find my message?

 

4.     Consider the DSA scheme implemented in the file “DSA.py”. The public parameters and public key are:

 

q = 18462870797958734358460540315802311963744999954506807981508498635091

p = 21844102112122237484058484990223222527816981702828279171498143036582716271485474028380542696862193720852272618397503658771128114568430034544311836848132556591324273117839115478343051538427437664722980830771161939139222964707695276957432968033365352302080366315415735532111302710857807281798249043320899027800135122873123243743524724602070457967657285884563858968187732680723369906222214201250288443824722261682828970158731587663585174032887767988219143996717380923998096794060064023264584949115354715211375168860544716843940259887168163262505413440632980952366656691935232538721726450037087263854935179798694999345517

g = 13843079639351340920273184714590884400432847093058770970775133079628015343474638985949514224469231316509301786191837239734743524804707156837615319355419215945094865320399756037490734275197507243978890158231379210099367755690209217652326933425758170008835084657241675545571324146202714002127571892258435472678396358353938476569410849475658691697420643000086724156167275855286708191941521213998074404126295230559090196852525498568126029906179168789585152438330622252753643553805877257623433974639379577436808678860489830511416186993204671106346196262903362008285485594747047950971109814842643611103016670841253194356243

public key - beta = 6187481213658176498787124123601684091780046690985227386674127034254039365850646655310542241724937514112519192485497669738105144173607992347626869972509174309127140941080651743898030456747633487761927322752193676176314211884662768871783260572354989592156755352437101758031330846064492530779348477298394716501400849788380847680039744807953192006233069850428367974025006391433578254859633968702925514987402010031888483663325943692618870576893826021018783543580318493456251127341437691102522482919743872855098214539426447960934626890138798345418250945885432084267499991534185991486840567366979305573275554091497155603826

 

You are given two signatures for two different message as follows:

 

(message1,   ,   ) = (b"He who laugh last didn't get the joke", 6164572993148268278544315246158794966061243456603081427389792698784, 2412874836775368230194957659405258449579579568340501217618177629780)

(message2,   ,   ) = (b"Ask me no questions, and I'll tell you no lies", 6164572993148268278544315246158794966061243456603081427389792698784, 343379365128270720539597367095485301128970178274104846189598795161)

 

Can you find my private key?

 

Bonus Question

 

5.     Consider the DSA scheme implemented in the file “DSA.py”. The public parameters and public key are:

 

q = 15141339084211537780798402821468668253233855293250282470707486523729

p = 15459352678170194999059797953835943703769299798522640485949251021230061239872933286596281671875036444766767260825161156339142374953144264667175663093532210016977000296281428180052962512096930034626707240943073909429948568647175489641923947055523690662397275499814011659615933313001220733558180164993086472379325887209418439076036830595968948122463542565488458285559269152814846930461678806155717771594791617514000333739836058367191702301817095873715810768950392576601345434651042282496258898798293897916341315693731763534513871295870117294672305447940132333142894162790759196704240972899412016593006223087871357404969

g = 3800569625008648766049545537807478639158256666453837543156865205157342453175195338293914518318389932512419197022492193267072466754594620461534567362497841710002599111953091344930343994503431071692400525354528547918075410538790275781900267312641988973075426468087022427855954288858299458927808889518984317490141729401786342725042250941182574740334793901912974170222604015177323368814264989835679407076289974855552414398779625521837257916022552980027627057473062644879659632681204107806120144998907991338913266334321160324651484012752441634140243465730939619242515280714356873699965985363402010686851443396200018800199

public key - beta = 13811718194912887731259973687531659017221233072693758339320677556085961091741512534312991319990988012320895125273138799484930424656328618986338233650799555131896857586001490595604365368085682743275712428137943225119715628405892357306029150574584119785832325605674838801154641895745311161271889436502899846458131900988387777254676157672199525938326470244363881227814557082187788046660952433631553517068095734365024876910709029416850114854064043338879940542901936624969303248595208108795751225387203405395739941042570698164719973037261394764330314120509607344408485820133307388882699955010320183318447065675487861322141

 

You are given two signatures for two different message as follows:

 

(message1,   ,   ) = (b"He who laugh last didn't get the joke", 7807207725923213670059456706077357545604668400924354746850607726310, 10137413521818981860558295844142463248736280669671376607939774420169)

(message2,   ,   ) = (b"Ask me no questions, and I'll tell you no lies", 13601517662990253244919392623006368173804524139680316147330845851641, 5354638027707905626045156057361096890377811387248394522419069236340)