Rate Region for Interactive Key Generation and Common Randomness Generation
Rate Region for Interactive Key Generation and Common Randomness Generation
复制标题
交互式密钥生成和公共随机性生成的速率区域
DOI:
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发表时间:
2016
期刊:
影响因子:
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通讯作者:
Jingbo Liu
中科院分区:
文献类型:
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作者:
Jingbo Liu
The purpose of this note is to provide a self-contained proof of a multi-letter characterization of the rate regions in interactive key generation and CR generation, as a supporting document for our recent work on certain single-letter characterization/bounds for the same problem [1]. The interactive CR generation problem is in several ways similar to interactive source coding [2]. Also, the multi-letter solutions for two-round CR generation [3, Theorem 4.2] or the minimum communication needed for maximum key rates [4, Theorem 4] are known. Although it is probable that the proofs of these special cases (based on typicality) can be extended to obtain the results in this note, we use the likelihood encoder [5] as an alternative proof technique which is technically simpler and applies to non-discrete alphabets. I. RELATION BETWEEN KEY GENERATION AND CR GENERATION (ASSUMING STOCHASTIC ENCODERS) • If (R,R1, R2) is achievable for key generation, then (R+R1 +R2, R1, R2) is achievable for CR generation. Indeed, we can assume that the communication messages in each round are asymptotically independent, since otherwise the achievability scheme of the source coding with side information problem implies that these messages can be compressed to satisfy the independence constraint. We can also assume that the communication rates in key generation are exactly R1 and R2, since otherwise we simply pad extra random bits to enlarge the communication rates. Then let CR = (key, communication) which has rate R+R1 +R2 because of the independence between the key and the communication. • If (R,R1, R2) is achievable for CR generation, then (R−R1−R2, R1, R2) is achievable for key generation: this is because using privacy amplification/leftover hash lemma (cf. Renner’s one-shot bound [6]), we can extract H(CR|communication) bits independent of communication asymptotically. (Future work: worth comparing one-shot bound from leftover hash with the one-shot bound directly from the likelihood encoder). The above observations imply that, asymptotically, CR generation and key generation are equivalent problems, so it suffices to prove the achievability and converse for CR generation which is conceptually simpler. II. MULTI-LETTER RATE REGIONS The rate regions for key generation and CR generation are characterized in this section.