Cryptanalysis

Break encryption algorithms

These tests will allow you to hone your cryptography skills. You will be faced with an encoded data. The challenge is to find the type of encoding or encryption and revert it back to find the solution.

Prerequisites:

– Knowledge of most common encoding formats.
– Knowledge of most common hash algorithms and ciphers.
– Knowledge of a scripting language.

75 Challenges

Results	Name	Validations	Number of points	Difficulty	Author	Note	Solution ↓↑	Date
	ECDSA - Implementation error	1% 69	100		Tosh		0	29 September 2019
	RSA - H-rabin	1% 91	60		Vozec		0	21 March 2023
	ElGamal - Fault attack (Introduction)	1% 36	35		Vozec		0	13 December 2024
	RSA - Padding	1% 297	35		Tosh		0	9 October 2016
	PHP - mt_rand	1% 175	40		NonStandardModel		0	28 March 2022
	RSA - Corrupted key 3	1% 197	40		blackndoor		0	5 September 2019
	DSA - Implementation error	1% 70	25		Vozec		0	13 December 2024
	FEAL - Differential Cryptanalysis	1% 51	50		Tosh		0	28 March 2022
	Goldreich Goldwasser Halevi \| Weak Parameter	1% 21	50		Vozec		0	13 December 2024
	AES - 4 Rounds	1% 367	35		Cryptanalyse		0	5 September 2018
	NTRU \| Multiple Transmission	1% 29	60		Vozec		0	13 December 2024
	NTRU \| Weak Parameter	1% 21	60		Vozec		0	13 December 2024
	Side Channel - AES : CPA	1% 91	50		cb34		0	28 March 2022
	Side Channel - AES : first round	1% 94	60		walafc0		0	28 March 2022
	AES-PMAC	1% 40	100		Cryptanalyse		0	26 May 2019
	Polyalphabetic substitution - One Time Pad	1% 386	60		Thanat0s		0	2 June 2013
	Shamir Secret Sharing - Reduction	1% 51	70		Vozec		0	5 February 2024
	Shamir Secret Sharing - Irreducible ?	1% 35	90		Mister7F		0	5 February 2024
	Service - Hash length extension attack	1% 1193	30		koma		1	19 August 2015
	RSA - Continued fractions	1% 1522	30		sambecks		1	8 September 2015
	Hash - DCC	3% 8844	5		Podalirius		1	13 July 2021
	Hash - DCC2	3% 8126	5		Podalirius		1	13 July 2021
	GEDEFU	1% 581	30		makhno		1	13 September 2016
	Hill Cipher	1% 228	30		LetMeR00t		1	21 March 2023
	RSA - Signature	1% 210	35		sar		1	9 March 2020
	Shamir Secret Sharing - Traitor	1% 104	35		Vozec		1	5 February 2024
	Hash - LM	3% 8591	5		Podalirius		1	13 July 2021
	RSA - Corrupted key 2	1% 333	40		blackndoor		1	11 January 2018
	AES - Fault attack #1	1% 202	50		Cryptanalyse		1	20 September 2018
	Hash - NT	2% 6936	5		Podalirius		1	13 July 2021
	AES - ECB - Copy Paste	1% 347	25		Vozec		1	5 February 2024
	AES - Fault attack #2	1% 145	80		Cryptanalyse		1	20 September 2018
	Hash - SHA-3	1% 164	75		Revenger		1	10 December 2016
	AES - Weaker variant	1% 151	70		Cryptanalyse		1	29 August 2018
	Encoding - Codebook	1% 447	20		n3rada		1	21 March 2023
	RSA - Lee cooper	1% 170	60		blackndoor , Synacktiv		1	7 November 2019
	Shamir Secret Sharing - Introduction	1% 360	30		Vozec		1	5 February 2024
	Service - CBC Padding	1% 1382	60		koma		2	4 October 2012
	AES128 - CTR	1% 736	40		Tosh		2	28 August 2015
	Enigma Machine	1% 276	50		peyman		2	12 October 2016
	ECDHE	1% 245	60		Tosh		2	20 November 2016
	ECDSA - Introduction	1% 341	35		Jrmbt		2	22 September 2019
	RSA - Corrupted key 1	1% 457	30		blackndoor		2	28 November 2017
	LFSR - Known plaintext	1% 1092	25		Brissouille		2	28 November 2017
	Twisted secret	1% 525	25		NonStandardModel		2	14 August 2020
	File - PKZIP 2	1% 345	20		kevin.mille		2	8 November 2024
	RSA - Common modulus	1% 2080	30		franb		3	24 December 2016
	CISCO - Salted Password	2% 5609	10		Tidusrose		3	13 July 2021
	White-Box Cryptography	1% 254	60		Cryptanalyse		3	21 October 2018
	Circular Bit Shift	1% 1747	20		BlackRaven		3	21 March 2023
	Polyalphabetic substitution - Vigenère	3% 10651	20		Arod		3	26 October 2011
	Discrete logarithm problem	1% 1332	40		RFC4949		3	8 June 2014
	OTP - Implementation error	1% 487	30		Podalirius		3	22 March 2021
	RSA - Decipher Oracle	1% 2092	25		Zweisamkeit		4	11 May 2017
	RSA - Multiple recipients	1% 1664	40		franb		4	29 November 2015
	AES - ECB	1% 2758	25		cez40		4	29 November 2015
	Hash - SHA-2	9% 32915	5		koma		4	3 June 2012
	Transposition - Rail Fence	2% 6657	20		YellowS4		4	6 April 2014
	RSA - Factorisation	2% 5117	25		HacKSpider		5	12 September 2010
	Monoalphabetic substitution - Caesar	5% 16962	15		Arod		5	22 October 2011
	Known plaintext - XOR	3% 9481	20		Ryscrow		5	3 February 2011
	Service - Timing attack	1% 2942	25		g0uZ , koma		5	28 October 2012
	System - Android lock pattern	2% 7070	20		Silentd		5	23 December 2012
	AES - CBC - Bit-Flipping Attack	1% 1692	25		Tie21		5	17 June 2018
	Code - Pseudo Random Number Generator	2% 3721	20		Tosh		6	19 December 2012
	Monoalphabetic substitution - Polybe	2% 3995	25		koma		6	6 December 2011
	File - PKZIP	4% 13457	15		g0uZ		6	30 August 2010
	Initialisation Vector	1% 2303	25		manticore , notfound404		6	25 August 2015
	File - Insecure storage 1	3% 9453	20		g0uZ		7	6 February 2012
	Hash - Message Digest 5	17% 62308	5		g0uZ		7	31 January 2010
	Encoding - UU	20% 71377	5		g0uZ		10	7 October 2006
	ELF64 - PID encryption	3% 8179	15		Lu33Y		10	8 February 2012
	Pixel Madness	5% 16433	15		Ryscrow		10	3 February 2011
	Shift cipher	6% 21171	10		m31z0nyx		10	16 February 2011
	Encoding - ASCII	26% 92726	5		Xartrick		10	4 December 2012

Challenge Results

Pseudo	Challenge	Lang	Date
ErVox90	Hash - SHA-2		21 July 2025 at 12:49
Dimitris	Encoding - ASCII		21 July 2025 at 12:48
LeGOAT	Hash - LM		21 July 2025 at 11:54
Kamaru	Hash - DCC		21 July 2025 at 11:52
LeGOAT	Hash - DCC2		21 July 2025 at 11:20
Nolwenn22	Clair connu - XOR		21 July 2025 at 11:06
Kamaru	Encodage - UU		21 July 2025 at 11:00
Kamaru	Encodage - ASCII		21 July 2025 at 10:58
yoav_s	DSA - Implementation error		21 July 2025 at 10:55
unescape455	Hash - DCC		21 July 2025 at 10:44