CUSTOMMediumCrypto

T-8000 (Sesame / Rice Radical Encoding)

XESXOR9/10/20263 min read

#crypto#custom#medium#brute_force_offset#cjk_offset_decode#linguistic_hint_decode#unicode_range_analysis

T-8000 (Sesame / Rice Radical Encoding)

Platform: taipanbyte | Category: Crypto | Type: Challenge | Difficulty: Medium | OS: NA | Author: XESXOR | Date: 2026-02-14 | Status: Solved Techniques: brute_force_offset, cjk_offset_decode, linguistic_hint_decode, unicode_range_analysis

Summary

T-8000 (Sesame / Rice Radical Encoding) — TaipanByte CTF

Description

Черно-белый. Семена. Масло. Индика. Сахар. Это что вообще? Ничего не понимаю...

籝籋粄簺籽籼籨簼籉籼粂籨籯簹类籨籼簹籵籿簼粆

Analysis

Step 1: Linguistic analysis of the hints

The description contains five Russian words that all describe properties of sesame (кунжут / 芝麻):

Hint	Translation	Connection to Sesame
Черно-белый	Black-white	Sesame seeds come in black and white varieties
Семена	Seeds	Sesame is a seed crop
Масло	Oil	Sesame oil is widely used
Индика	Indica	Sesamum indicum — the botanical name
Сахар	Sugar	Sesame is used in sweets (halva, kozinaki)
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This points to a "sesame encoding" — an encoding scheme using CJK characters related to grain/rice.

Step 2: Unicode analysis of the encoded text

All 22 Chinese characters fall within a narrow Unicode range U+7C39 to U+7C86. They all share the 米 (rice/grain) radical, which is thematically connected to sesame (a grain/seed crop):

籝=0x7C5D  籋=0x7C4B  粄=0x7C84  簺=0x7C3A  籽=0x7C7D  籼=0x7C7C
籨=0x7C68  簼=0x7C3C  籉=0x7C49  籼=0x7C7C  粂=0x7C82  籨=0x7C68
籯=0x7C6F  簹=0x7C39  类=0x7C7B  籨=0x7C68  籼=0x7C7C  簹=0x7C39
籵=0x7C75  籿=0x7C7F  簼=0x7C3C  粆=0x7C86

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Key observations:

All codepoints share the prefix 0x7C
The range spans only 77 values (0x39 to 0x86) — exactly covering printable ASCII
This strongly suggests a simple offset-based encoding

Step 3: Finding the decoding offset

Since the flag format is TB{...}, we know:

First character 籝 (U+7C5D) must map to T (ASCII 84 = 0x54)
Offset = 0x7C5D - 0x54 = 0x7C09

Decoding formula: ASCII = Unicode_codepoint - 0x7C09

Character-by-character decoding

Character	Codepoint	- 0x7C09	ASCII	Char
籝	U+7C5D	84	0x54	`T`
籋	U+7C4B	66	0x42	`B`
粄	U+7C84	123	0x7B	`{`
簺	U+7C3A	49	0x31	`1`
籽	U+7C7D	116	0x74	`t`
籼	U+7C7C	115	0x73	`s`
籨	U+7C68	95	0x5F	`_`
簼	U+7C3C	51	0x33	`3`
籉	U+7C49	64	0x40	`@`
籼	U+7C7C	115	0x73	`s`
粂	U+7C82	121	0x79	`y`
籨	U+7C68	95	0x5F	`_`
籯	U+7C6F	102	0x66	`f`
簹	U+7C39	48	0x30	`0`
类	U+7C7B	114	0x72	`r`
籨	U+7C68	95	0x5F	`_`
籼	U+7C7C	115	0x73	`s`
簹	U+7C39	48	0x30	`0`
籵	U+7C75	108	0x6C	`l`
籿	U+7C7F	118	0x76	`v`
簼	U+7C3C	51	0x33	`3`
粆	U+7C86	125	0x7D	`}`
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Solution

 python read-only • copy allowed
#!/usr/bin/env python3
"""
T-8000 — TaipanByte CTF
Sesame encoding: CJK characters from 米 (rice) radical mapped to ASCII
via fixed offset 0x7C09.
"""

text = "籝籋粄簺籽籼籨簼籉籼粂籨籯簹类籨籼簹籵籿簼粆"
flag = ''.join(chr(ord(ch) - 0x7C09) for ch in text)
print(flag)  # TB{REDACTED}

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