6 ms·

Isn't the issue here that the security chip is on the screen vs the motherboard? Given a screen is probably 100x more likely to break this is consumer hostile

by nikau 5y ago

Isn't the issue here that the security chip is on the screen vs the motherboard? Given a screen is probably 100x more likely to break this is consumer hostile engineering.

oneplane 5y ago
I doubt that it is as simple as that. Designing modern technology is incredibly hard, then running that design through a process that makes it viable for mass production is almost as hard. In both of those steps there might be tons of reasons to have it in one place or another. Imagine the following scenarios: - It has been found that during assembly units that do not pass QA often has this chip fail, and thus making it easily swappable increases the production yield during assembly instead of PCBA. - To create a security boundary for biometric data, as a rule the assembly that captures the data and authenticates it has to be separate from the application processor assembly. Swapping either then cannot be done surreptitiously. That makes the chip's job part of the screen assembly and not something else. - A cost reducing measure between the sensor and the data processing chip over a high-speed serial connection turned out to be removal of buffers or transceivers but this meant that the signal lines had to be shorter and sandwiched against a large ground plane to ensure signal integrity and prevent frequent retransmissions. "Hostile" engineering (which is not a word I would choose) would be any kind of security screw that doesn't improve over other screws. Think of normal Torx (which is excellent) vs. "security" Torx, or Apple's Pentalobe. Those exist for one reason: to deter the average user from undoing those screws. The reason for deterrence vary, in some cases it's just a reduction of liability ("we made it harder so that Joe Bloggs has to be really sure he wants to screw up his device, therefore we are not liable for his screwed up device"), sometimes theft ("we'll use security Torx screws on those coat hangers in the toilet stalls, that way the teens don't steal them to sell them on the black market"), sometimes it's some weird protection scheme that never works ("if we make the screws just a tiny bit harder to find a bit for, they will have to come to us and we'll have to deal with all of their problems instead"). In most mass-market cases it generally boils down to liability and scalability. And waiving liability as a middle ground often doesn't exist because it doesn't scale well. What does help is making it part of a brand's identity or marketing, that way the budget doesn't have to come out of any of the general product lifecycle budgets which then makes it seem to have the same bottom line which is the whole reason for-profit companies exist.
- nikau 5y ago
  > It has been found that during assembly units that do not pass QA often has this chip fail, and thus making it easily swappable increases the production yield during assembly instead of PCBA. Yet its on the second most expensive part of the BOM, so nope. > To create a security boundary for biometric data, as a rule the assembly that captures the data and authenticates it has to be separate from the application processor assembly. Swapping either then cannot be done surreptitiously. That makes the chip's job part of the screen assembly and not something else. The chip can be unsoldered, so nope > cost reducing measure between the sensor and the data processing chip over a high-speed serial connection turned out to be removal of buffers or transceivers but this meant that the signal lines had to be shorter and sandwiched against a large ground plane to ensure signal integrity and prevent frequent retransmissions. Its on a mylar flex cable, so nope Its just apple being pricks, much like requiring custom SCSI drive strings on generic hard disks back in the classic mac era, nothing has changed.
  - oneplane 5y ago
    It seems you have missed the point so hard it's almost pointless to reply. The cases are theoretical cases, not direct one-on-one practical reasons why this specific chip on this specific assembly was built in this specific way. We don't have the data and we never will. We can't read minds, and all there seems to be is speculation and anthropomorphisation of corporations which is pointless beyond reason. Unless you have some design-for-manufacture experience, taking part in this discussion is moot anyway. It doesn't matter if the specific part has a special BOM cost, what matters is that the production flow is not interrupted. Assemblies that do not pass QA aren't tossed, but the final product needs to come off the line anyway, so swapping out the assembly in that phase while returning it to some other process for inspection is the normal thing to do. You can't do that thing if the assembly is a flip-chip or BGA on a PCBA without swapping the entire board which while still possible to cover in a separate process is much more expensive in validation and repair than re-attaching a flat-flex with a new BGA or flip-chip part on it using what is essentially a glorified hotbar machine. If Apple was a person and the person wanted to be a prick, there are far cheaper and easier ways to do that. Fill the entire phone with epoxy, problem solved. Would be instantly water-proof, shock-resistant, and if you cover it in a fine wire mesh and connect some SRAM with ephemeral keys to it you can make it super secure by never being able to extract any data from it. But Apple isn't a person, it's a company. It's not your friend or your enemy, it's just a machine designed to make money. Real-world requirements apply, and they trump pettiness for the sake of pettiness. Inducing friction to their own customers is just a liability factor, and if you think that is new you got a whole world of pain to explore.

by nikau 5y ago

Isn't the issue here that the security chip is on the screen vs the motherboard? Given a screen is probably 100x more likely to break this is consumer hostile engineering.

oneplane 5y ago

I doubt that it is as simple as that. Designing modern technology is incredibly hard, then running that design through a process that makes it viable for mass production is almost as hard. In both of those steps there might be tons of reasons to have it in one place or another. Imagine the following scenarios: - It has been found that during assembly units that do not pass QA often has this chip fail, and thus making it easily swappable increases the production yield during assembly instead of PCBA. - To create a security boundary for biometric data, as a rule the assembly that captures the data and authenticates it has to be separate from the application processor assembly. Swapping either then cannot be done surreptitiously. That makes the chip's job part of the screen assembly and not something else. - A cost reducing measure between the sensor and the data processing chip over a high-speed serial connection turned out to be removal of buffers or transceivers but this meant that the signal lines had to be shorter and sandwiched against a large ground plane to ensure signal integrity and prevent frequent retransmissions. "Hostile" engineering (which is not a word I would choose) would be any kind of security screw that doesn't improve over other screws. Think of normal Torx (which is excellent) vs. "security" Torx, or Apple's Pentalobe. Those exist for one reason: to deter the average user from undoing those screws. The reason for deterrence vary, in some cases it's just a reduction of liability ("we made it harder so that Joe Bloggs has to be really sure he wants to screw up his device, therefore we are not liable for his screwed up device"), sometimes theft ("we'll use security Torx screws on those coat hangers in the toilet stalls, that way the teens don't steal them to sell them on the black market"), sometimes it's some weird protection scheme that never works ("if we make the screws just a tiny bit harder to find a bit for, they will have to come to us and we'll have to deal with all of their problems instead"). In most mass-market cases it generally boils down to liability and scalability. And waiving liability as a middle ground often doesn't exist because it doesn't scale well. What does help is making it part of a brand's identity or marketing, that way the budget doesn't have to come out of any of the general product lifecycle budgets which then makes it seem to have the same bottom line which is the whole reason for-profit companies exist.

nikau 5y ago
> It has been found that during assembly units that do not pass QA often has this chip fail, and thus making it easily swappable increases the production yield during assembly instead of PCBA. Yet its on the second most expensive part of the BOM, so nope. > To create a security boundary for biometric data, as a rule the assembly that captures the data and authenticates it has to be separate from the application processor assembly. Swapping either then cannot be done surreptitiously. That makes the chip's job part of the screen assembly and not something else. The chip can be unsoldered, so nope > cost reducing measure between the sensor and the data processing chip over a high-speed serial connection turned out to be removal of buffers or transceivers but this meant that the signal lines had to be shorter and sandwiched against a large ground plane to ensure signal integrity and prevent frequent retransmissions. Its on a mylar flex cable, so nope Its just apple being pricks, much like requiring custom SCSI drive strings on generic hard disks back in the classic mac era, nothing has changed.
- oneplane 5y ago
  It seems you have missed the point so hard it's almost pointless to reply. The cases are theoretical cases, not direct one-on-one practical reasons why this specific chip on this specific assembly was built in this specific way. We don't have the data and we never will. We can't read minds, and all there seems to be is speculation and anthropomorphisation of corporations which is pointless beyond reason. Unless you have some design-for-manufacture experience, taking part in this discussion is moot anyway. It doesn't matter if the specific part has a special BOM cost, what matters is that the production flow is not interrupted. Assemblies that do not pass QA aren't tossed, but the final product needs to come off the line anyway, so swapping out the assembly in that phase while returning it to some other process for inspection is the normal thing to do. You can't do that thing if the assembly is a flip-chip or BGA on a PCBA without swapping the entire board which while still possible to cover in a separate process is much more expensive in validation and repair than re-attaching a flat-flex with a new BGA or flip-chip part on it using what is essentially a glorified hotbar machine. If Apple was a person and the person wanted to be a prick, there are far cheaper and easier ways to do that. Fill the entire phone with epoxy, problem solved. Would be instantly water-proof, shock-resistant, and if you cover it in a fine wire mesh and connect some SRAM with ephemeral keys to it you can make it super secure by never being able to extract any data from it. But Apple isn't a person, it's a company. It's not your friend or your enemy, it's just a machine designed to make money. Real-world requirements apply, and they trump pettiness for the sake of pettiness. Inducing friction to their own customers is just a liability factor, and if you think that is new you got a whole world of pain to explore.