[3] Later, in 2005, he helped show that a DRM system called Extended Copy Protection functioned identically to a rootkit and weakened the security of computers in which audio CDs were played.

The technique, which was initially effective against nearly every full-disk encryption product on the market, exploits DRAM data remanence to retrieve memory contents even after the device has been briefly powered off.

[4] One version of the technique involves cooling DRAM modules with freeze spray to slow data decay, then removing them from the computer and reading them in an external device.

It has become an important part of computer forensics practice and has also inspired a wide variety of defensive research, such as leakage-resilient cryptography and hardware implementations of encrypted RAM.

In 2011, Halderman and his students invented Telex, a new approach to circumventing Internet censorship, partially by placing anticensorship technology into core network infrastructure outside the censoring country.

[9] In 2012, Halderman and coauthors discovered serious flaws in random number generators that weakened the public-key cryptography used for HTTPS and SSH servers in millions of Internet of things devices.

Since they worked by exploiting remnants of ways in which older versions of the protocol had been deliberately weakened due to 1990s-era restrictions on the export of cryptography from the United States,[16] they carried lessons for the ongoing public policy debate about cryptographic back doors for law enforcement.

[17] Halderman's Logjam work also provided a plausible explanation for a major question raised by the Edward Snowden revelations: how the National Security Agency could be decoding large volumes of encrypted network traffic.

By extrapolating their results to the resources of a major government, the researchers concluded that nation-state attackers could plausibly break 1,024-bit Diffie-Hellman key exchange using a purpose-built supercomputer.

In partnership with Google, Halderman's research group used ZMap to study the security of email delivery,[25] highlighting seven countries where more than 20% of inbound Gmail messages arrived unencrypted due to network attackers.

"[32] In 2015, Halderman was part of a team of proponents that included Steven M. Bellovin, Matt Blaze, Nadia Heninger, and Andrea M. Matwyshyn who successfully proposed a security research exemption to Section 1201 of the Digital Millennium Copyright Act.

[9] After the 2016 United States presidential election, computer scientists, including Halderman, urged the Clinton campaign to request an election recount in Wisconsin, Michigan, and Pennsylvania (three swing states where Trump had won narrowly, while Clinton won New Hampshire and Maine narrowly) for the purpose of excluding the possibility that the hacking of electronic voting machines had influenced the recorded outcome.