jm + reversing + reverse-engineering   2

'Leak of the secret German Internet Censorship URL blacklist BPjM-Modul'.

Turns out there's a blocklist of adult-only or prohibited domains issued by a German government department, The Federal Department for Media Harmful to Young Persons (German: "Bundesprüfstelle für jugendgefährdende Medien" or BPjM), issued in the form of a list of hashes of those domains. These were extracted from an AVM router, then the hashes were brute forced using several other plaintext URL blocklists and domain lists.

Needless to say, there's an assortment of silly false positives, such as the listing of the website for the 1997 3D Realms game "Shadow Warrior":
hashes  reversing  reverse-engineering  germany  german  bpjm  filtering  blocklists  blacklists  avm  domains  censorship  fps 
july 2014 by jm
Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35
Amazing reverse engineering.
In a hotel room in Texas, Clive Sinclair had a big problem. He wanted to sell a cheap scientific calculator that would grab the market from expensive calculators such as the popular HP-35. Hewlett-Packard had taken two years, 20 engineers, and a million dollars to design the HP-35, which used 5 complex chips and sold for $395. Sinclair's partnership with calculator manufacturer Bowmar had gone nowhere. Now Texas Instruments offered him an inexpensive calculator chip that could barely do four-function math. Could he use this chip to build a $100 scientific calculator?
Texas Instruments' engineers said this was impossible - their chip only had 3 storage registers, no subroutine calls, and no storage for constants such as π. The ROM storage in the calculator held only 320 instructions, just enough for basic arithmetic. How could they possibly squeeze any scientific functions into this chip?

Fortunately Clive Sinclair, head of Sinclair Radionics, had a secret weapon - programming whiz and math PhD Nigel Searle. In a few days in Texas, they came up with new algorithms and wrote the code for the world's first single-chip scientific calculator, somehow programming sine, cosine, tangent, arcsine, arccos, arctan, log, and exponentiation into the chip. The engineers at Texas Instruments were amazed.

How did they do it? Up until now it's been a mystery. But through reverse engineering, I've determined the exact algorithms and implemented a simulator that runs the calculator's actual code. The reverse-engineered code along with my detailed comments is in the window below.
reversing  reverse-engineering  history  calculators  sinclair  ti  hp  chips  silicon  hacks 
august 2013 by jm

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