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Arpit Bhayani Blogs
001 Ai Topological Sort

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TLDR: ETAOIN SHRDLU - Using Letter Frequency to Decipher the Ciphered

Date: 2020-06-21 Source: https://arpitbhayani.me/blogs/decipher-single-xor

Overview

Crack single-byte XOR ciphers! Learn how to decipher encrypted messages without the key using frequency analysis and Python. Encryption is a process of encoding messages such that it can only be read and understood by the intended parties.

Key Points

  • Encryption is a process of encoding messages such that it can only be read and understood by the intended parties.
  • Encryption: As part of the encryption process, the original message is iterated bytewise and every single byte b is XORed with the encryption key key and the resultant stream of bytes is again translated back as characters and sent to the other party.
  • Decryption: Decryption is the process of extracting the original message from the encrypted ciphertext given the encryption key.
  • Bruteforce: There are a very limited number of possible encryption keys - 256 to be exact - we can, very conveniently, go for the Bruteforce approach and try to decrypt the ciphered text with every single one of it.
001-ai-topological-sort.md
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002 Temporal Primer
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003 Rag Production
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004 Structure Of Llm Chat
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005 How Llms Work
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006 Monolith Is Distributed System
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007 Defensive Databases
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008 Bm25
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009 Join Algorithms
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010 Venting At Work
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011 Half Life
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012 Multi Paxos
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013 Mysql Replication Internals
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014 Bloom Filters
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017 Product Quantization
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018 Qkv Matrices
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019 Deleted Production
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020 How Llm Inference Works
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021 Blocking Queues
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022 Heartbeats In Distributed Systems
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024 Redis Replication
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036 Cpu Cache Locality
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037 Eventual Consistency
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039 Masters
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051 Promotions Are Proactive Not Reactive
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098 Find Your Own Project
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100 Keep Yourself Unblocked
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102 Pseudorandom Number Generation Lfsr
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105 Data Partitioning
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108 Conflict Detection
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109 Multi Master Replication
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110 Monotonic Reads
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113 Replication Formats
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114 Replication Strategies
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115 Master Replica Replication
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116 Durability
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117 Isolation
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119 Consistency
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121 Mistaken Beliefs Of Distributed Systems
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127 Persistent Data Structures Introduction
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130 Recursion Visualizer Python
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136 Ts Smoothing
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142 10x Engineer
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144 Decipher Single Xor
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145 Python Iterable Integers
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146 Inheritance C
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147 Rum
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156 Idf
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158 Python Prompts
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159 Rule 30 Cellular Automata
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160 Function Overloading
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161 Isolation Forest
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162 Image Steganography
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163 Long Integers Python
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164 I Changed My Python
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165 Benchmark And Compare Pagination Approach In Mongodb
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166 Mongodb Cursor Skip Is Slow
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167 Fast And Efficient Pagination In Mongodb
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168 Making Http Requests Using Netcat
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  • ETAOIN SHRDLU: Letter Frequency is the number of times letters of an alphabet appear on average in written language.
  • Fitting Quotient: Fitting Quotient is the measure that suggests how well the two Letter Frequency Distributions match.

    • Takeaway

    Now that we have everything we require to directly get the plain text out of the given ciphertext we wrap it in a function that iterates over all possible encryption keys in the range 0, 256), decrypts the ciphertext, computes the fitting quotient for the plain text and returns the one that minimizes the quotient as the original message.