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sam henri gold (@[email protected])

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 1d

btw this does not help my case in a design career. nobody has ever said “yeah he’s great for design but I wish he had working knowledge of reverse engineering binaries and was hellbent on figuring out stupid bullshit from 15 years ago”
https://hachyderm.io/@samhenrigold/115330105694760262

Attached: 2 images hey wanna see something kinda interesting? this was the entire fix to the iPhone Antennagate in 2010. 20 bytes. (this is going to be a very long thread 🧵)

hachyderm.io

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

oh also in 4.0.1 they changed the height of the lower bars to be taller lmao

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sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

So there ya go. 20 bytes.

This has concluded a Tech Thread. Back to shitposting.

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

In 4.0.1, they changed these values to be way smoother. Mapped onto a chart, you can see that it takes a lot to drop from 5 to 0 bars. It’s harder to see 5 bars, but it’s harder to plummet bars.

• 0x86FFFFFF equals −122 dBm — 1 bar threshold.
• 0x98FFFFFF equals −104 dBm — 2 bars threshold.
• 0x9EFFFFFF equals −98 dBm — 3 bars threshold.
• 0xA7FFFFFF equals −89 dBm — 4 bars threshold.
• 0xB0FFFFFF equals −80 dBm — 5 bars threshold.

4.0 and 4.0.1 signal bar thresholds mapped onto each other. The 4.0 line jumps from 0 to full bars in a fairly short span compared to 4.0.1

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sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

When you plot this onto a chart, you can see how the values are kinda screwed up since the values are really optimistic. Most of the time, you would see 4-5 bars. But when you gripped it, since the falloff is so sharp, you’d see a catastrophic drop from 5 to 2 bars.

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

...this is. This is the lookup table. When you convert the bytes to actual dBm values, you get:
-115, -111, -107, -103, and -99

(the closer to zero, the better the signal)

For example, here you need -107 or better signal to see 3 bars.

the raw bytes of the lookup table from 4.0

Five threshold values for signal bars.
- 0x8DFFFFFF equals −115 dBm, marking the 1-bar threshold.
- 0x91FFFFFF equals −111 dBm, 2-bar threshold.
- 0x95FFFFFF equals −107 dBm, 3-bar threshold.
- 0x99FFFFFF equals −103 dBm, 4-bar threshold.
- 0x9DFFFFFF equals −99 dBm, 5-bar threshold.

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

The actual calculation is dead simple. When converting signal strength to bars, CommCenter loads each threshold from memory and compares until it finds the right range.

This code is not the problem...

$Some hideous assembly code that boils down to: bar_count = /* initial r4 */; while (bar_count != 5) { if (RSSI <= threshold[bar_count]) break; bar_count++; }$

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

I downloaded both firmwares and started poking around. In the CoreTelephony framework, I found a promising looking binary: CommCenter. Looking at the strings gave me a pretty good sense that this is where the bar formula was.

strings CommCenter | grep -i bars

UseEcn0Bars
ecn0 is %d / signal is %d, assuming 5 bars
ecn0 is %d / signal is %d, assuming 4 bars
ecn0 is %d / signal is %d, we say %d bars
telling UI to draw %d bars, %d signal

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sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

For context, back in 2010 when the iPhone 4 came out, people noticed you could grip the phone in a certain way and the signal bars would plummet from 5 to, like, 2.

A few weeks later, they published a letter ( […]

[Original post on hachyderm.io]

Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength. For example, we sometimes display 4 bars when we should be displaying as few as 2 bars. Users observing a drop of several bars when they grip their iPhone in a certain way are most likely in an area with very weak signal strength, but they don’t know it because we are erroneously displaying 4 or 5 bars. Their big drop in bars is because their high bars were never real in the first place.

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

hey wanna see something kinda interesting? this was the entire fix to the iPhone Antennagate in 2010. 20 bytes.

(this is going to be a very long thread 🧵)

Assembly code between iOS 4.0 and 4.0.1. It's basically the same except one instruction points to a different address.

A lookup table tweaked between 4.0 and 4.0.1.

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sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

i do weddings btw

Reposted by sam henri gold

Mastodon @mastodon.mastodon.social.ap.brid.gy · 2d

We appreciate that certain politicians have recently admitted their naivete in entrusting the voices of their governments to corporate / for-profit social media.

To these politicians, we say: https://joinmastodon.org/hosting

Managed Mastodon

joinmastodon.org

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sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

@tay Do the TLS and talk with your certs

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

HTTP code 3OH3: She wants to touch me (whoa) She wants to love me (whoa) She'll never leave me (whoa, whoa, oh, oh)

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 2d

at the end of the day, what is “spineless” if not “boneless”. spineless wings, boneless politicians

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 3d

George Bluth: there’s a good chance I may have committed some light undocumented API usage

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 4d

cannot believe we're gonna have to say goodbye to this man

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 4d

oh work

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 4d

omg i just started watching The Good Wife and just realized that the lady in the show…IS THE GOOD WIFE 🤯🤯 follow for more tv insider trivia

sam henri gold @samhenrigold.hachyderm.io.ap.brid.gy · 4d

just realized i haven’t seen stars in a while. like the sky ones. wonder if those are still a thing.