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Unhackable Cryptography?

A recent article overhyped the release of EverCrypt, a cryptography library created using formal methods to prove security against specific attacks.

The Quantum magazine article sets off a series of “snake-oil” alarm bells. The author’s Github README is more measured and accurate, and illustrates what a cool project this really is. But it’s not “hacker-proof cryptographic code.”

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CAs Reissue Over One Million Weak Certificates

Turns out that the software a bunch of CAs used to generate public-key certificates was flawed: they created random serial numbers with only 63 bits instead of the required 64. That may not seem like a big deal to the layman, but that one bit change means that the serial numbers only have half the required entropy. This really isn’t a security problem; the serial numbers are to protect against attacks that involve weak hash functions, and we don’t allow those weak hash functions anymore. Still, it’s a good thing that the CAs are reissuing the certificates. The point of a standard is that it’s to be followed.

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I Was Cited in a Court Decision

An article I co-wrote — my first law journal article — was cited by the Massachusetts Supreme Judicial Court — the state supreme court — in a case on compelled decryption.

Here’s the first, in footnote 1:

We understand the word “password” to be synonymous with other terms that cell phone users may be familiar with, such as Personal Identification Number or “passcode.” Each term refers to the personalized combination of letters or digits that, when manually entered by the user, “unlocks” a cell phone. For simplicity, we use “password” throughout. See generally, Kerr & Schneier, Encryption Workarounds, 106 Geo. L.J. 989, 990, 994, 998 (2018).

And here’s the second, in footnote 5:

We recognize that ordinary cell phone users are likely unfamiliar with the complexities of encryption technology. For instance, although entering a password “unlocks” a cell phone, the password itself is not the “encryption key” that decrypts the cell phone’s contents. See Kerr & Schneier, supra at 995. Rather, “entering the [password] decrypts the [encryption] key, enabling the key to be processed and unlocking the phone. This two-stage process is invisible to the casual user.” Id. Because the technical details of encryption technology do not play a role in our analysis, they are not worth belaboring. Accordingly, we treat the entry of a password as effectively decrypting the contents of a cell phone. For a more detailed discussion of encryption technology, see generally Kerr & Schneier, supra.

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On the Security of Password Managers

There’s new research on the security of password managers, specifically 1Password, Dashlane, KeePass, and Lastpass. This work specifically looks at password leakage on the host computer. That is, does the password manager accidentally leave plaintext copies of the password lying around memory?

All password managers we examined sufficiently secured user secrets while in a “not running” state. That is, if a password database were to be extracted from disk and if a strong master password was used, then brute forcing of a password manager would be computationally prohibitive.

Each password manager also attempted to scrub secrets from memory. But residual buffers remained that contained secrets, most likely due to memory leaks, lost memory references, or complex GUI frameworks which do not expose internal memory management mechanisms to sanitize secrets.

This was most evident in 1Password7 where secrets, including the master password and its associated secret key, were present in both a locked and unlocked state. This is in contrast to 1Password4, where at most, a single entry is exposed in a “running unlocked” state and the master password exists in memory in an obfuscated form, but is easily recoverable. If 1Password4 scrubbed the master password memory region upon successful unlocking, it would comply with all proposed security guarantees we outlined earlier.

This paper is not meant to criticize specific password manager implementations; however, it is to establish a reasonable minimum baseline which all password managers should comply with. It is evident that attempts are made to scrub and sensitive memory in all password managers. However, each password manager fails in implementing proper secrets sanitization for various reasons.

For example:

LastPass obfuscates the master password while users are typing in the entry, and when the password manager enters an unlocked state, database entries are only decrypted into memory when there is user interaction. However, ISE reported that these entries persist in memory after the software enters a locked state. It was also possible for the researchers to extract the master password and interacted-with password entries due to a memory leak.

KeePass scrubs the master password from memory and is not recoverable. However, errors in workflows permitted the researchers from extracting credential entries which have been interacted with. In the case of Windows APIs, sometimes, various memory buffers which contain decrypted entries may not be scrubbed correctly.

Whether this is a big deal or not depends on whether you consider your computer to be trusted.

Several people have emailed me to ask why my own Password Safe was not included in the evaluation, and whether it has the same vulnerabilities. My guess about the former is that Password Safe isn’t as popular as the others. (This is for two reasons: 1) I don’t publicize it very much, and 2) it doesn’t have an easy way to synchronize passwords across devices or otherwise store password data in the cloud.) As to the latter: we tried to code Password Safe not to leave plaintext passwords lying around in memory.

So, Independent Security Evaluators: take a look at Password Safe.

Also, remember the vulnerabilities found in many cloud-based password managers back in 2014?

News article. Slashdot thread.

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Hacking the GCHQ Backdoor

Last week, I evaluated the security of a recent GCHQ backdoor proposal for communications systems. Furthering the debate, Nate Cardozo and Seth Schoen of EFF explain how this sort of backdoor can be detected:

In fact, we think when the ghost feature is active­ — silently inserting a secret eavesdropping member into an otherwise end-to-end encrypted conversation in the manner described by the GCHQ authors­ — it could be detected (by the target as well as certain third parties) with at least four different techniques: binary reverse engineering, cryptographic side channels, network-traffic analysis, and crash log analysis. Further, crash log analysis could lead unrelated third parties to find evidence of the ghost in use, and it’s even possible that binary reverse engineering could lead researchers to find ways to disable the ghost capability on the client side. It should be obvious that none of these possibilities are desirable for law enforcement or society as a whole. And while we’ve theorized some types of mitigations that might make the ghost less detectable by particular techniques, they could also impose considerable costs to the network when deployed at the necessary scale, as well as creating new potential security risks or detection methods.

Other critiques of the system were written by Susan Landau and Matthew Green.

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El Chapo’s Encryption Defeated by Turning His IT Consultant

Impressive police work:

In a daring move that placed his life in danger, the I.T. consultant eventually gave the F.B.I. his system’s secret encryption keys in 2011 after he had moved the network’s servers from Canada to the Netherlands during what he told the cartel’s leaders was a routine upgrade.

A Dutch article says that it’s a BlackBerry system.

El Chapo had his IT person install “…spyware called FlexiSPY on the ‘special phones’ he had given to his wife, Emma Coronel Aispuro, as well as to two of his lovers, including one who was a former Mexican lawmaker.” That same software was used by the FBI when his IT person turned over the keys. Yet again we learn the lesson that a backdoor can be used against you.

And it doesn’t have to be with the IT person’s permission. A good intelligence agency can use the IT person’s authorizations without his knowledge or consent. This is why the NSA hunts sysadmins.

Slashdot thread. Hacker News thread. Boing Boing post.

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Alex Stamos on Content Moderation and Security

Former Facebook CISO Alex Stamos argues that increasing political pressure on social media platforms to moderate content will give them a pretext to turn all end-to-end crypto off — which would be more profitable for them and bad for society.

If we ask tech companies to fix ancient societal ills that are now reflected online with moderation, then we will end up with huge, democratically-unaccountable organizations controlling our lives in ways we never intended. And those ills will still exist below the surface.

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