Cryogenic Machining: Custom Rubber Parts

Cryogenic Machining Custom Rubber Parts

Fashioning a custom, one-off rubber part for your project isn’t usually an option, but [Ben Krasnow] has an alternative to injection molding and casting: machining frozen rubber.

As [Ben] points out, you can’t exactly pop a sheet of rubber on your mill and CNC the needed shape; the bit will push the material around rather than cut it. Freezing the rubber first, however, allows you to carve into the now-hardened material.

His initial setup consisted of a sheet of aluminum with water drizzled on top, a square of neoprene placed on the water, and a steady stream of -60 to -80C alcohol flowing directly onto the rubber. The water underneath freezes, holding the neoprene in place. This proved problematic as the ice-clamp gives way before the milling is complete. [Ben] later adds some bolts to clamp the pieces down, allowing the milling process finish as planned.

A small plastic tray sits underneath this assembly to capture the alcohol as it runs off, feeding it back with some tubing. [Ben] recommends against a submersible aquarium pump—his initial choice—because the pump stopped working after a few minutes immersed in the chilly alcohol. An external, magnetically-driven pump solved the problem although it does require manual priming.

Stick around after the jump for the video and check out some of [Ben's] other projects, like his quest for the perfect cookie, or CT scanning a turkey.

[Read more...]

Freezing Android to crack the encryption

frozen-phone-encryption-hacking

Build a better lock and someone will make a tool to open it without the key. Or in this case they’ve made a tool to discover the key using a trip to through the deep freeze. The Forensic Recovery of Scrambled Telephones — or FROST — uses cold temperatures and a custom recovery image to crack Android encryption keys.

Cold boot hacks go way back. They leverage use of low temperatures to slow down the RAM in a device. In this case, the target phone must already be powered on. Booting a phone that uses the encryption offered by Android 4.0 and newer requires the owner’s pass code to decrypt the user partition. But it then remains usable until the next power cycle. By freezing the phone, then very quickly disconnecting and reconnecting the battery, researchers were able to flash their own recovery image without having the encryption key cleared from RAM. As you can see above, that recovery package can snoop for the key in several different ways.

[Thanks Rob]

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