Cracking SIM cards with side-channel attacks

This entry was posted on Tuesday, August 11th, 2015.

A Jiao Tong University researcher has exploited side-channel attack techniques to crack the encryption codes protecting 3G and 4G cards.

“[The cards use] AES-128, which is supposed to be virtually unbeatable by a brute-force attack, but turns out to be easy to defeat using side-channel analysis,” explained Iain Thomson of The Register. “Side-channel attacks measure things like power consumption, electromagnetic emissions and heat generation to work out what is going on in a chip. The technique has been around for years, and requires physical access to the target device.”


As Thomson reports, Yu Yu and his university team tracked power levels using an oscilloscope, monitored data traffic with an MP300-SC2 protocol analyzer and correlated the results with a SIM card reader and a standard PC.

“With this simple setup they cracked eight commercial SIM cards in between 10 and 80 minutes,” said Thomson. “Yu [also] demonstrated how the cloned SIM card can successfully impersonate the owner in class [and] showed how a cloned card could change the password on an Alipay and potentially drain the account.”

According to Yu, the above-mentioned hack is based on known differential power analysis attacks.

“The move to AES-based encryption algorithms in 3G/4G USIM cards did not systematically take advantage of state-of-the-art countermeasures against side-channel attacks,” he added. “Indeed, the USIM cards we analyzed essentially relied on plain (unprotected) software implementations of the AES.”

Helena Handschuh, a Director at Rambus’ Cryptography Research division, co-designed the MILENAGE standard discussed in Yu’s Black Hat paper. According to Handschuh, AES-128/Rijndael was chosen for MILENAGE in 2001 so that side-channel countermeasures could be easily incorporated in a SIM-class platform.

“Yu Yu’s paper demonstrates once again that, even though these algorithms are mathematically strong and unbroken, all implementers of crypto need to be aware of side-channel attacks and take appropriate steps to mitigate them,” Handschuh concluded.

As we’ve previously discussed on Rambus Press, physical electronic systems routinely leak information about the internal process of computing. In practical terms, this means attackers can exploit various side-channel techniques to gather data and extract secret cryptographic keys.

As such, the Rambus Cryptography Research division has designed a range of DPA countermeasures that offer a combination of software, hardware and protocol techniques specifically designed to protect tamper-resistant devices from side-channel attacks. These include leak reduction, incorporating randomness, generating amplitude and temporal noise, as well as executing protocol-level countermeasures.

Interested in learning more about how Rambus is helping to secure SoCs, devices and content? You can read more about our DPA countermeasures here, CryptoFireWall Cores here and CryptoManager platform here.