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arXiv 2009.10060cs.CRcs.GT
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密码强度信令:一种针对密码破解的反直觉防御

Password Strength Signaling: A Counter-Intuitive Defense Against Password Cracking

Wenjie Bai, Jeremiah Blocki, Ben Harsha

摘要:

我们引入密码强度信息信令作为一种新颖的,但反直觉的,防御机制,对密码破解攻击。最近的违规行为使数十亿用户密码暴露在离线密码破解攻击的危险威胁中。离线攻击者可以快速检查数百万(有时数十亿/万亿)的密码猜测,方法是将其哈希值与从被破坏的身份验证服务器窃取的哈希值进行比较。攻击者只受到他愿意投入的资源的限制。我们的关键思想是让认证服务器存储一个关于每个用户密码强度的(噪声)信号,以便离线攻击者找到。令人惊讶的是,我们表明,信号的噪声分布往往可以调整,使一个理性的(利润最大化)攻击者将破解更少的密码。信令方案利用了密码破解不是零和游戏的事实,即,攻击者的利润是由破解的密码的值减去总猜测成本给出的。因此,一个定义良好的信令策略将鼓励攻击者通过破解更少的密码来减少他的猜测成本。我们使用进化算法来计算最佳的信号方案的后卫。作为一个概念验证,我们评估我们的机制在几个密码数据集,并表明它可以减少破解密码的总数高达$12\%$(分别。$5\%$)的所有用户在防御离线(分别为在线)攻击。

英文摘要:

We introduce password strength information signaling as a novel, yet counter-intuitive, defense mechanism against password cracking attacks. Recent breaches have exposed billions of user passwords to the dangerous threat of offline password cracking attacks. An offline attacker can quickly check millions (or sometimes billions/trillions) of password guesses by comparing their hash value with the stolen hash from a breached authentication server. The attacker is limited only by the resources he is willing to invest. Our key idea is to have the authentication server store a (noisy) signal about the strength of each user password for an offline attacker to find. Surprisingly, we show that the noise distribution for the signal can often be tuned so that a rational (profit-maximizing) attacker will crack fewer passwords. The signaling scheme exploits the fact that password cracking is not a zero-sum game i.e., the attacker's profit is given by the value of the cracked passwords minus the total guessing cost. Thus, a well-defined signaling strategy will encourage the attacker to reduce his guessing costs by cracking fewer passwords. We use an evolutionary algorithm to compute the optimal signaling scheme for the defender. As a proof-of-concept, we evaluate our mechanism on several password datasets and show that it can reduce the total number of cracked passwords by up to $12\%$ (resp. $5\%$) of all users in defending against offline (resp. online) attacks.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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