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arXiv 2103.15009cs.CRquant-ph
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不可克隆加密,再访

Unclonable Encryption, Revisited

Prabhanjan Ananth, Fatih Kaleoglu

摘要:

不可克隆加密是由Broadbent和Lord(TQC'20)提出的一种加密方案,它具有以下引人注目的功能:给定一个密文,攻击者不能创建两个密文,这两个密文都解密成与原始密文相同的消息。我们重新审视这个概念,并显示以下内容:-可重用性:由Broadbent和主提出的结构有一个缺点,即它们要么保证一次性的安全性(即,加密密钥只能使用一次加密消息)在平原模型或他们保证安全的随机预言模型。构造了具有语义安全性的不可克隆加密方案。我们提出了两个结构(公钥和私钥设置)从最小的密码学假设。- 下界和广义构造:我们重新审视Broadbent和Lord的信息论一次性安全构造。攻击者在构建过程中的成功概率被保证为$0.85^n$,其中$n$是消息的长度。理解$0.5^n$的理想成功概率(可以忽略不计地接近)是否无法实现是很有趣的。我们推广他们的建设是基于更广泛的一类一夫一妻制的纠缠游戏。我们证明了一个简单的克隆攻击,成功的概率$0.71^n$对一类计划,包括Broadbent和主。我们还提出了一个$0.75^n$克隆攻击专门针对他们的计划。- 版权保护的含义:我们表明,不可克隆加密,满足一个更强的属性,称为不可克隆的不可复制性(定义的布罗德本特和主),意味着复制保护一个简单的类不可学习的功能。虽然我们目前还没有满足这个更强属性的加密方案,但这一含义展示了构建复制保护的新途径。

英文摘要:

Unclonable encryption, introduced by Broadbent and Lord (TQC'20), is an encryption scheme with the following attractive feature: given a ciphertext, an adversary cannot create two ciphertexts both of which decrypt to the same message as the original ciphertext. We revisit this notion and show the following: - Reusability: The constructions proposed by Broadbent and Lord have the disadvantage that they either guarantee one-time security (that is, the encryption key can only be used once to encrypt the message) in the plain model or they guaranteed security in the random oracle model. We construct unclonable encryption schemes with semantic security. We present two constructions (for public-key and private-key settings) from minimal cryptographic assumptions. - Lower Bound and Generalized Construction: We revisit the information-theoretic one-time secure construction of Broadbent and Lord. The success probability of the adversary in their construction was guaranteed to be $0.85^n$, where $n$ is the length of the message. It was interesting to understand whether the ideal success probability of (negligibly close to) $0.5^n$ was unattainable. We generalize their construction to be based on a broader class of monogamy of entanglement games. We demonstrate a simple cloning attack that succeeds with probability $0.71^n$ against a class of schemes including that of Broadbent and Lord. We also present a $0.75^n$ cloning attack exclusively against their scheme. - Implication to Copy-Protection: We show that unclonable encryption, satisfying a stronger property, called unclonable-indistinguishability (defined by Broadbent and Lord), implies copy-protection for a simple class of unlearnable functions. While we currently don't have encryption schemes satisfying this stronger property, this implication demonstrates a new path to construct copy-protection.

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