Vernam encryption

honggarae 02/04/2022 849

Thesynonym“One-Time-Pad”generallyreferstoVernamencryptionmethod.Themostimportantthinghereisthatoncethetransformedinputciphertextisused,thisinputciphertextisnolongerusedinanyothermessages(soitisaone-time).Thelengthoftheinputciphertextisequaltothelengthoftheoriginalmessageplaintext.

Steps

Thefollowingarethemainsteps.

1.Treateachplaintextletterasanumberinincreasingorder,A=0,B=1,etc..

2.Dothesametreatmentforeachletterintheinputplaintext.

3.Addeachletterintheplaintexttothecorrespondingletterinthekey.

4.Ifthesumisgreaterthan26,subtract26fromit.

5.Convertthesumintoletterstogettheciphertext.

Vernam encryption

Obviously,becauseTheone-timeboardisusedupandmustbegivenup,sothistechnologyisquitesafeandsuitableforasmallamountofcleartextmessages,butitdoesnotworkforlargemessages(theone-offboardiscalledKey(Key),andthecleartexthasThekeyisaslongasitis,soitdoesn’tworkforbigmessages.)TheVernamencryptionmethodwasoriginallyimplementedbyAT&Twiththehelpoftheso-calledVernammachine.

AssumingthattheplaintextmessageHOWAREYOUisperformedVermanencryption,theone-timeboardistheciphertextmessageUQXTQUYFRobtainedbyNCBTZQARX.Thefollowingisanillustration

1.Plaintext:HOWAREYOU

714220174241420

2.KeyNCBTZQARX

132119251601723

3.Initialsum201623194220243143

4.Ifgreaterthan25,subtract2620162319162024517

5.CiphertextUQXTQUYFR

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