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B-SIDE

A daily CTF challenge with a fun new puzzle every day

What is B-SIDE?

This side program features challenges with a different flavor from Daily AlpacaHack. We publish one harder or more unconventional challenge every few days.

Join Anytime

Solve each challenge within its time window to appear on the leaderboard.

Not a Competition

Discussion with friends or AI is welcome (account sharing is prohibited).

Solution Sharing Rules

Sharing solutions is allowed only after the challenge period has ended.

New to CTFs?

This program features higher difficulty and unconventional challenges. Try the beginner-friendly Daily AlpacaHack first to warm up.

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Today's Challenge
minaminaominaminao
Complete RSA
Crypto
Hard
7 solves
Submissions (latest 3)
rsk0315

SOLVED!

Jun 20, 5:48 PM

Leaderboard
Upcoming challenges reveal the , , and in advance.
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Jun 2026

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Upcoming
Mon
Tue
Wed
Thu
Fri
Sat
Sun
1-5
minaminaominaminao
vanished
Misc
Very Hard
27 solves
6-9
tchentchen
YAuth
Misc
Hard
21 solves
 
tchentchen
YAuth
Misc
Hard
21 solves
10-15
ptr-yudaiptr-yudai
Gloinks
Misc
Very Very Hard
14 solves
 
ptr-yudaiptr-yudai
Gloinks
Misc
Very Very Hard
14 solves
16-20
tchentchen
InstaTalk
Web
Very Hard
20 solves
21-25
minaminaominaminao
Complete RSA
Crypto
Hard
7 solves
 
minaminaominaminao
Complete RSA
Crypto
Hard
7 solves
26
Coming soon
27
Coming soon
28
Coming soon
29
Coming soon
30
Coming soon
1
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Writeups

tchen

Writeup for YAuth

tchen

author
en
YAuth

7 hours ago

tchen

Writeup for Iframe Sandbox

author
en

7 hours ago

tchen

Writeup for Bulk Note

author
en

7 hours ago

「AIには解けない」と言われたAlpacaHack B-sideを、Codexで20時間かけて解いた

ja

2026/06/15 16:16

kirehash

Writeup for vanished

ja

2026/06/11 14:51

minaminao

Writeup for vanished

author
ja

2026/06/08 17:24

Rows:

Bulk Note

Topic: YAMLReleased: Apr 22, 2026

29 solves
WebMisc
Hard

by

tchen

tchen

Writeups

tchen

Writeup for Bulk Note

tchen

author
en

7 hours ago


hxuu

Writeup for Bulk Note

en

2026/05/22 23:25



tadanobutubutu

Writeup for Bulk Note

ja

2026/04/25 19:11

descriptionsolveswriteups