cryptography: keeping secrets using algebra and geometry
TRANSCRIPT
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Cryptography: Keeping Secrets Using Algebra and GeometryAndré MathurinBellarmine College Preparatory (San Jose, CA)
Contact & Resource Information
[email protected]://tinyurl.com/Crypto-NCTM2014
With the increasing reliance on e-mail and texting, how canmathematics help ensure that these communications remain private?Come learn ways to do so and get ideas for engaging students in thebasic ideas of cryptography within the context of algebra andgeometry topics.
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PreliminariesGoals
Spark Ideas for Teaching Functions Introduce Cryptography using Algebra & Geometry
Format Audience Participation + Presenter GuidanceHighlight Connections/Extensions
Disclaimers Requires Modular Arithmetic Do Not Expect Highly Secure
Cryptography: Keeping Secrets Using Algebra & Geometry
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Make the phrase “show me the math”difficult to read by scrambling up the letters.
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Make the phrase “show me the math”difficult to read by scrambling up the letters.
VS.
• Which side is more difficult to read? (Cryptography)
• How many different scrambles are possible? (Combinatorics)
• Which of the scramble is the worst/best? (Cryptography)
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
The Best
• Disadvantages to this method? (Cryptography)
Random Scramble MethodWrite each letter on a slip of paper, put slips in a hat, and
randomly select one at a time.
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble This Phrase
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Scrambled Version
The Unscrambled Version
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
How do you get this
from this?
• What is the a pattern? (Cryptanalysis)
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Scramble Methodcreates a pseudo‐random “mixing up” of the phrase
Define the function as the character that appears in the th position of the message.
1,2,3,4,5,6,7,8,9,10,11,12,13 , , , , , , ,
example:
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Scramble Methodcreates a pseudo‐random “mixing up” of the phrase
1,2,3,4,5,6,7,8,9,10,11,12,13 1,2,3,4,5,6,7,8,9,10,11,12,13
example:
Define the function as a scramble of the position values .
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Scramble Method
example:
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Scramble Methodpseudo‐random scramble of the phrase characters
5 13
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Scramble the phrase “inverse functions”
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Scramble the phrase “inverse functions”
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Un‐Scramble MethodUse
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Un‐Scramble Method
example:
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Modular Un‐Scramble Method
)
8 13
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble the phrase
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AlgebraCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble the phrase
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GeometryCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble This Phrase
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GeometryCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble This Phrase
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GeometryCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble This Phrase
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GeometryCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Unscramble This Phrase
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GeometryCryptography: Keeping Secrets
Scramble It! (aka Transposition)
Scramble the Phrase“Cryptography can become addictive”
• How many different ways are there? (Combinatorics)• What other shapes could you use? (Number Theory)
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AlgebraCryptography: Keeping Secrets
Replace It! (aka Substitution)
Disguise a message by replacing characters
Define a function for converting characters to numbers
, , , , , … , , , 1,2,3,4,5, … , 24,25,26
example:
• How is this similar to before? (Functions)• How is this different than before? (Functions)
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AlgebraCryptography: Keeping Secrets
Replace It! (aka Substitution)
Disguise a message by replacing characters
Compose functions to replace characters with characters
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AlgebraCryptography: Keeping Secrets
Replace It! (aka Substitution)
Disguise a message by replacing characters
Compose functions to replace characters with characters
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