정보보호입문 CaesarCypherAlgorithm
- 최초 등록일
- 2013.11.14
- 최종 저작일
- 2013.04
- 5페이지/ MS 워드
- 가격 2,000원
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본문내용
English Alphabet Frequency Attack on Caesar Cipher Algorithm:
Initial State: Ciphertext = { Tg tmmtvd pabva nmbebsxl max xqblmxgvx hy dghpg ietbgmxqm tgw vbiaxkmxqm itbkl bl vteexw t dghpg ietbgmxqm tmmtvd }
Input: Ciphertext of English Alphabet = { C1, C2, …., Cn } and Unknown Key k (n=96 letters)
input1) Given(Known) ciphertext = { Tg tmmtvd pabva nmbebsxl max xqblmxgvx hy dghpg ietbgmxqm tgw vbiaxkmxqm itbkl bl vteexw t dghpg ietbgmxqm tmmtvd }
input 2) Unknown key k
input 3) Given(known) English Alphabet Frequency Table =>'E' is at the top
Step0) Initialize fk ← 0 for all k = 0,…,25
f0<-0, f1<-0, ..., f25<-0
Step1) for each i = 1,2,…n, do
Iteration I=1)
Substep1) Xi ← Ci
C1='T'-> X1=19
Substep2) If Xi = k, then fk ← fk + 1
X1=19 then f19=f19+1=0+1=1
Iteration I=2)
Substep1) Xi ← Ci
C2='g'-> X2=6
Substep2) If Xi = k, then fk ← fk + 1
X2=6 then f6=f6+1=0+1=1
Iteration I=3)
Substep1) Xi ← Ci
C1='t'-> X1=19
Substep2) If Xi = k, then fk ← fk + 1
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참고 자료
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