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Security. SIMs are smartcards - separate systems storing cryptographic material and performing trusted operations. A TPM that can be plugged and unplugged, bas

Security. SIMs are smartcards - separate systems storing cryptographic material and performing trusted operations. A TPM that can be plugged and unplugged, basically, using the same standards as a chip-and-pin credit card. Equivalent keystores haven't been available built in to cell phones until the last few years.

jeroenhd 4y ago
TrustZone and Secure Element have been available for quite some time now. I think this problem is more because carriers/users don't want to give up control to software companies than it's about lacking hardware.
- azernik 4y ago
  TrustZone is iffy security-wise, and built-in SEs have only been available for iPhones and the highest-end quarter or so of Android phones until recently.
- dfox 4y ago
  What apple calls Secure Element is a separate chip that essentially is an eSIM with NFC interface (or in other words, smart card MCU with larger memory and more IO). Apple's implementation of what TrustZone is supposed to solve is called Secure Enclave and also involves separate CPU core (inside the application SoC) that is isolated from the application cores by how the hierarchy of various buses on the chip is structured. I assume that there are two reasons why it is done this way instead of software/weird-CPU-state solutions (like TrustZone): this construction is easier to reason about and at least in the Secure Element case easier to certify to the requirements of card issuers (as it is essentially standard off-the-shelf secure MCU).
  - jeroenhd 4y ago
    I agree that a separate secure chip is a superior option to TrustZone. However, if TrustZone is good enough for authorising bank transfers, it's also good enough for me. Security chips have also had their vulnerabilities over the years, through power injection attacks or similar, that allow cloning just like bypassing the security of TrustZone would. The attack may be harder to pull off, but nothing is unhackable.
- rsaxvc 4y ago
  With the continued development of specex attacks, having those features in a separate domain reduces the attack surface some, compared to sharing a core with attacker controlled code.
- lxgr 4y ago
  The eSIM is a secure element! TrustZone is a technology building block, not a complete implementation. You couldn't simply run a SIM on TrustZone, but you probably can use it to implement an eSIM execution environment, which seems to be what Qualcomm is actually doing here.

jeroenhd 4y ago

TrustZone and Secure Element have been available for quite some time now. I think this problem is more because carriers/users don't want to give up control to software companies than it's about lacking hardware.

azernik 4y ago
TrustZone is iffy security-wise, and built-in SEs have only been available for iPhones and the highest-end quarter or so of Android phones until recently.
dfox 4y ago
What apple calls Secure Element is a separate chip that essentially is an eSIM with NFC interface (or in other words, smart card MCU with larger memory and more IO). Apple's implementation of what TrustZone is supposed to solve is called Secure Enclave and also involves separate CPU core (inside the application SoC) that is isolated from the application cores by how the hierarchy of various buses on the chip is structured. I assume that there are two reasons why it is done this way instead of software/weird-CPU-state solutions (like TrustZone): this construction is easier to reason about and at least in the Secure Element case easier to certify to the requirements of card issuers (as it is essentially standard off-the-shelf secure MCU).
- jeroenhd 4y ago
  I agree that a separate secure chip is a superior option to TrustZone. However, if TrustZone is good enough for authorising bank transfers, it's also good enough for me. Security chips have also had their vulnerabilities over the years, through power injection attacks or similar, that allow cloning just like bypassing the security of TrustZone would. The attack may be harder to pull off, but nothing is unhackable.
rsaxvc 4y ago
With the continued development of specex attacks, having those features in a separate domain reduces the attack surface some, compared to sharing a core with attacker controlled code.
lxgr 4y ago
The eSIM is a secure element! TrustZone is a technology building block, not a complete implementation. You couldn't simply run a SIM on TrustZone, but you probably can use it to implement an eSIM execution environment, which seems to be what Qualcomm is actually doing here.