AES - 2026 ACF Regionals

Packet J: Bonus 8

Modern devices often implement this cipher in hardware to both increase speed and decrease the attack surface for timing-related side-channel attacks. For 10 points each:

[10m] What cipher won a competition by NIST (“nist”) in 2001 to become the most commonly used standard cipher?

ANSWER: AES [or Advanced Encryption Standard; or Rijndael (“RINE-dale”)]

[10h] Block ciphers like AES can be used to construct this other type of cipher, which include the Chacha and Salsa20 ciphers. These ciphers encrypt plaintext bit by bit by XORing them with an encrypted sequence of characters.

ANSWER: stream ciphers

[10e] The encrypted keystream in a stream cipher must have this property to ensure the ciphertext is unpredictable. An insecure method of generating numbers with this property may rely on the system clock as an initial seed.

ANSWER: pseudorandomness [or randomness; accept random number generation or pseudorandom number generation; accept stochasticity; prompt on RNG or PRNG by asking “what does that stand for?”]

<Illinois B, Other Science> | Packet J - Southampton A, Indiana A, Illinois B, Edinburgh A

Heard	PPB	E %	M %	H %
81	11.60	98%	14%	5%

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Conversion

Team	Opponent	Part 1	Part 2	Part 3	Total	Parts
Alabama A	Louisville B	0	0	10	10	E
Berkeley B	Berkeley A	0	0	10	10	E
Berkeley C	Berkeley D	10	0	10	20	ME
Binghamton B	Binghamton A	0	0	10	10	E
Bruin	WashU A	0	0	10	10	E
CWRU A	Michigan C	0	0	10	10	E
Carleton University	UBC B	0	0	10	10	E
Catholic	Maryland B	0	0	10	10	E
Central Florida A	Florida A	0	0	10	10	E
Central Florida C	Florida B	0	0	10	10	E
Chicago A	Chicago E	0	0	10	10	E
Chicago B	Illinois A	0	0	10	10	E
Chicago C	Purdue B	10	0	10	20	ME
Chicago D	Northwestern D	0	0	10	10	E
City St. George's	Cambridge B	0	0	10	10	E
Claremont	Washington B	10	0	10	20	ME
Columbia A	Johns Hopkins A	0	0	10	10	E
Columbia C	Rutgers B	10	0	10	20	ME
Cornell A	Cornell B	0	0	10	10	E
Cornell C	Rochester	0	0	10	10	E
Dartmouth A	Brandeis A	10	10	10	30	MHE
Dartmouth B	Brown	0	0	10	10	E
Duke	North Carolina A	0	0	10	10	E
Durham	Oxford B	0	0	10	10	E
Edinburgh B	Bristol	0	0	10	10	E
Florida C	Central Florida B	0	0	10	10	E
Georgetown	Swarthmore	0	0	10	10	E
Georgia Tech A	Minnesota A	0	0	10	10	E
Georgia Tech C	Georgia Tech B	0	0	10	10	E
Guelph	Toronto E	0	0	10	10	E
Harvard B	Brandeis B	0	0	10	10	E
Illinois C	Indiana C	10	0	10	20	ME
Imperial A	UCL	0	0	10	10	E
Indiana B	Northwestern B	0	0	10	10	E
John Jay	Johns Hopkins B	0	0	10	10	E
LSE	Cambridge C	0	0	10	10	E
Liberty A	North Carolina B	0	0	10	10	E
Louisville A	Vanderbilt B	0	0	10	10	E
MIT	Yale	10	0	10	20	ME
McGill B	Brock	0	0	10	10	E
McMaster A	Queen's	0	0	10	10	E
Michigan A	Ohio State B	0	0	10	10	E
Michigan B	Michigan State	0	0	10	10	E
Mississipi State	Alabama B	0	0	10	10	E
Missouri B	Carleton College	0	0	10	10	E
NC State A	Liberty B	0	10	10	20	HE
NYU A	Maryland A	0	0	10	10	E
NYU B	Columbia B	0	0	10	10	E
North Carolina C	Virginia Tech A	0	0	10	10	E
Notre Dame A	Northwestern C	0	0	10	10	E
Ohio State A	Ohio State C	0	0	10	10	E
Oxford A	Imperial C	0	0	10	10	E
Penn State	RIT	0	0	10	10	E
Pittsburgh	CWRU B	0	0	10	10	E
Purdue A	Notre Dame B	10	0	10	20	ME
Rutgers A	Maryland C	0	0	10	10	E
Simon Fraser	Toronto C	0	0	10	10	E
South Carolina B	James Madison B	0	0	0	0
Southern Connecticut State	Harvard A	0	0	10	10	E
Stanford B	Stanford A	0	0	10	10	E
Tennessee A	Georgia Tech D	0	0	10	10	E
Tennessee B	Sewanee	0	0	10	10	E
Texas A	Texas B	0	0	10	10	E
Texas A&M A	Murray State A	0	0	10	10	E
Toronto B	Ottawa	0	0	10	10	E
Toronto D	Toronto Metropolitan	0	0	10	10	E
Toronto F	McMaster B	0	0	10	10	E
Toronto G	Western C	0	0	10	10	E
UCLA A	UC Irvine	0	0	10	10	E
UCLA B	Arizona State	0	0	10	10	E
UCSD A	UCSD B	10	10	10	30	MHE
UCSD C	UC Santa Barbara	0	0	10	10	E
Vassar	NYU C	0	0	10	10	E
Virginia	James Madison A	0	0	10	10	E
Virginia Tech B	South Carolina A	0	0	10	10	E
Wake Forest	NC State B	0	0	10	10	E
WashU B	Kentucky	0	10	0	10	H
Waterloo A	UBC A	10	0	10	20	ME
Waterloo B	McGill A	10	0	10	20	ME
Western A	Western B	0	0	10	10	E
William and Mary	VCU	0	0	10	10	E

Summary

Tournament	Edition	Match	Heard	PPB	E %	M %	H %
California (North)	Main Site	✓	3	13.33	100%	33%	0%
California (South)	Main Site	✓	4	15.00	100%	25%	25%
Canada	Main Site	✓	12	11.67	100%	17%	0%
Florida	Main Site	✓	3	10.00	100%	0%	0%
Great Lakes	Main Site	✓	5	10.00	100%	0%	0%
Lower Mid-Atlantic	Main Site	✓	9	10.00	89%	0%	11%
Midwest	Main Site	✓	8	13.75	100%	38%	0%
Northeast	Main Site	✓	5	16.00	100%	40%	20%
Overflow	Main Site	✓	3	13.33	100%	33%	0%
South Central	Main Site	✓	2	10.00	100%	0%	0%
Southeast	Main Site	✓	8	10.00	88%	0%	13%
UK	Main Site	✓	6	10.00	100%	0%	0%
Upper Mid-Atlantic	Main Site	✓	9	11.11	100%	11%	0%
Upstate NY	Main Site	✓	4	10.00	100%	0%	0%