Cryptography

The Numbers [50 pts]

Description

The numbers... what do they mean?

Solution

Given 16 9 3 15 3 20 6 { = picoCTF [given that is the format] 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 a b c d e f g h i j k l m n o p q r s t u v w x y z Thus 20 8 5 14 21 13 2 5 18 19 13 1 19 15 14 } = thenumbersmason}

Flag: PICOCTF{THENUMBERSMASON}

Easy1 [100 pts] [Not Solved]

Description

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?.

Solution

a

Flag:

13 [100 pts]

Description

Cryptography can be easy, do you know what ROT13 is? cvpbPGS{abg_gbb_onq_bs_n_ceboyrz}

Solution

I could just go to an online converter, BUT I decided to write the code myself.

enc_message = 'cvpbPGS{abg_gbb_onq_bs_n_ceboyrz}'
message = ""
rot = 13
alphabet = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
for c in enc_message:
	try:
		index = alphabet.index(c)
		new_letter = alphabet[(index + rot )% len(alphabet)]
		if index < 26: # Fix mismatched casing
			message += new_letter.lower()
		elif index > 26:
			message += new_letter.upper()
	except: # Doesn't exist in alphabet
		message += c
		continue
print(message)

Flag: picoCTF{not_too_bad_of_a_problem}

caesar [100 pts]

Description

Decrypt this message.

Solution

Reusing the code from earlier with a little modification because we need to try all possibilities to get to this point I made this code

enc_message = '{dspttjohuifsvcjdpoabrkttds}'
alphabet = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
for shift in range(0, 26): # Shift 1 to 25 letters (26 would be no shift)
	message = ''
	for c in enc_message:
		try:
			index = alphabet.index(c)
			new_letter = alphabet[(index + shift)% len(alphabet)]
			if index < 26: # Fix mismatched casing
				message += new_letter.lower()
			elif index > 26:
				message += new_letter.upper()
		except: # Doesn't exist in alphabet
			message += c
			continue
	print(str(shift) + " " + message)

Flag: picoCTF{crossingtherubiconzaqjsscr}

la cifra de [200 pts] [Not Solved]

Description

I found this cipher in an old book. Can you figure out what it says? Connect with nc jupiter.challenges.picoctf.org 32411.

Solution

When type in the command it returns

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_h1ah3x7g996649}

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.

Flag:

Tapping [200 pts]

Description

Theres tapping coming in from the wires. What's it saying nc jupiter.challenges.picoctf.org 21610.

Solution

Hmmm, let me just guess Morse code maybe. Connecting it gives an easy impression with .--. .. -.-. --- -.-. - ..-. { -- ----- .-. ... ...-- -.-. ----- -.. ...-- .---- ... ..-. ..- -. ...-- ----. ----- ..--- ----- .---- ----. ..... .---- ----. } Which put into Cyber Chef comes out the flag. (Note to do this you have to remove the {})

Flag: PICOCTF{M0RS3C0D31SFUN3902019519}

Flags [200 pts] [Not Solved]

Description

What do the flags mean?

Solution

a

Flag:

Mr-Worldwide [200 pts] [Not Solved]

Description

A musician left us a message. What's it mean?

Solution

a

Flag:

rsa-pop-quiz [200 pts] [Not Solved]

Description

Class, take your seats! It's PRIME-time for a quiz... nc jupiter.challenges.picoctf.org 58617

Solution

a

Flag:

waves over lambda [300 pts] [Not Solved]

Description

We made a lot of substitutions to encrypt this. Can you decrypt it? Connect with nc jupiter.challenges.picoctf.org 43522.

Solution

a

Flag:

miniRSA [300 pts] [Not Solved]

Description

Let's decrypt this: ciphertext? Something seems a bit small.

Solution

a

Flag:

b00tl3gRSA2 [400 pts] [Not Solved]

Description

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 19566.

Solution

a

Flag:

AES-ABC [400 pts] [Not Solved]

Description

AES-ECB is bad, so I rolled my own cipher block chaining mechanism - Addition Block Chaining! You can find the source here: aes-abc.py. The AES-ABC flag is body.enc.ppm

Solution

a

Flag:

b00tl3gRSA3 [450 pts] [Not Solved]

Description

Why use p and q when I can use more? Connect with nc jupiter.challenges.picoctf.org 4557.

Solution

a

Flag:

john_pollard [500 pts] [Not Solved]

Description

Sometimes RSA certificates are breakable

Solution

a

Flag: