“Hello Bob, Alice”---Secure wireless communication with

mutual link information(a tutorial perspective)

Dr. Shaoen WuSchool of Computing

http://networks.cs.usm.edu

Shaoen.wu@usm.edu

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Outline

• Information Security 101• Wireless Channel Characteristics• Wireless Physical Security

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Outline

• Information Security 101• Wireless Channel Characteristics• Wireless Physical Security

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Security Model

• Secrecy / Confidentiality

• Authentication / Integrity

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Encryption

• Conventional Encryption (Shared Key Encryption,

Symmetric Encryption)

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Encryption

• Public-Private Key Encryption (PKI, asymmetric

encryption)

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Encryption

• Shared Key – Fast– Hard in key distribution

• PKI– Slow– Easy in key distribution

• But require infrastructure

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Wireless Communication

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Channel uncorrelated at different locations

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Wireless Communication

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Channel reciprocity

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Wireless Signal Symbol

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)()( wtjAety

Key Generation

• Metrics– Channel Response; Received Signal Strength,

Phase

• Goals (controversial)– fast– strong

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Generation Procedures

• Probing / Sampling

• Quantization

• Information Reconciliation

• Privacy Amplification

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Design Issues• Probing

– time duplex• Interpolation ---finite impulse response (FIR) fractional delay

filter

– Time selective– Frequency selective

• Sampling– Autocorrelation -- key strength– Frequency (open question)

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Design Issues• Quantization

– More levels, more bits, but less agreement

• Information Reconciliation --- key agreement• hash (verification) + exhaustive search (correction)– Correction codes– interactive information reconciliation protocol

• Privacy Amplification– Leftover hash lemma04/22/23 14

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