TY - JOUR
T1 - Secret sharing over infinite domains
AU - Chor, Benny
AU - Kushilevitz, Eyal
PY - 1993/6
Y1 - 1993/6
N2 - Let ℱn be a monotone, nontrivial family of sets over {1, 2, …, n}. An ℱn perfect secret-sharing scheme is a probabilistic mapping of a secret to n shares, such that: The secret can be reconstructed from any set T of shares such that T ∈ ℱn. No subset T ∉ ℱn of shares reveals any partial information about the secret. Various secret-sharing schemes have been proposed, and applications in diverse contexts were found. In all these cases the set of secrets and the set of shares are finite. In this paper we study the possibility of secret-sharing schemes over infinite domains. The major case of interest is when the secrets and the shares are taken from a countable set, for example all binary strings. We show that no ℱn secret-sharing scheme over any countable domain exists (for any n ≥ 2). One consequence of this impossibility result is that no perfect private-key encryption schemes, over the set of all strings, exist. Stated informally, this means that there is no way to encrypt all strings perfectly without revealing information about their length. These impossibility results are stated and proved not only for perfect secret-sharing and private-key encryption schemes, but also for wider classes—weak secret-sharing and private-key encryption schemes. We constrast these results with the case where both the secrets and the shares are real numbers. Simple perfect secret-sharing schemes (and perfect private-key encryption schemes) are presented. Thus, infinity alone does not rule out the possibility of secret sharing.
AB - Let ℱn be a monotone, nontrivial family of sets over {1, 2, …, n}. An ℱn perfect secret-sharing scheme is a probabilistic mapping of a secret to n shares, such that: The secret can be reconstructed from any set T of shares such that T ∈ ℱn. No subset T ∉ ℱn of shares reveals any partial information about the secret. Various secret-sharing schemes have been proposed, and applications in diverse contexts were found. In all these cases the set of secrets and the set of shares are finite. In this paper we study the possibility of secret-sharing schemes over infinite domains. The major case of interest is when the secrets and the shares are taken from a countable set, for example all binary strings. We show that no ℱn secret-sharing scheme over any countable domain exists (for any n ≥ 2). One consequence of this impossibility result is that no perfect private-key encryption schemes, over the set of all strings, exist. Stated informally, this means that there is no way to encrypt all strings perfectly without revealing information about their length. These impossibility results are stated and proved not only for perfect secret-sharing and private-key encryption schemes, but also for wider classes—weak secret-sharing and private-key encryption schemes. We constrast these results with the case where both the secrets and the shares are real numbers. Simple perfect secret-sharing schemes (and perfect private-key encryption schemes) are presented. Thus, infinity alone does not rule out the possibility of secret sharing.
KW - Perfect private-key encryption
KW - Secret sharing
UR - http://www.scopus.com/inward/record.url?scp=0027239099&partnerID=8YFLogxK
U2 - 10.1007/BF02620136
DO - 10.1007/BF02620136
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AN - SCOPUS:0027239099
SN - 0933-2790
VL - 6
SP - 87
EP - 95
JO - Journal of Cryptology
JF - Journal of Cryptology
IS - 2
ER -