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Show HN: PunchCard Key Backup

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Re: Show HN: PunchCard Key Backup

#31

Post by stavros »

im_down_w_otp wrote: post #30
stavros wrote: post #13

Earlier quoted context omitted.

Thus defeating the entire purpose! Unless you plan to wipe your router's firmware after every one.

The CNC router's firmware? The CNC controller itself is dumb as hell. It's connected via serial to an old offline computer that's only job is to pipe G-code over RS-232. Not even to "load a program" to hold in memory on the controller. Literally to stream the commands to the machine.

My CNC controller has an SD card, Wifi, Bluetooth, and USB. They're not all the same.

Re: Show HN: PunchCard Key Backup

#32

Post by ivanjermakov »

neilv wrote: post #26

I like the survivability, and the constraint to be doable with common hand tools. For more information density, and easier readability by a less-technical person who inherits it -- at the cost of requiring special tools -- I wonder about using number&letter stamps with a hammer. Or, if you permit very special tools, laser-cut alphanumerics (base16, base58, or base64, for arbitrary bits; or alphabetic passphrases). Ei…

Agree, going from binary to a higher base, e.g null, hole, + and -, would increase information density drastically (in 256 times in this case).

Re: Show HN: PunchCard Key Backup

#35

Post by im_down_w_otp »

stavros wrote: post #31
im_down_w_otp wrote: post #30

Earlier quoted context omitted.

The CNC router's firmware? The CNC controller itself is dumb as hell. It's connected via serial to an old offline computer that's only job is to pipe G-code over RS-232. Not even to "load a program" to hold in memory on the controller. Literally to stream the commands to the machine.

My CNC controller has an SD card, Wifi, Bluetooth, and USB. They're not all the same.

Fancy!

Re: Show HN: PunchCard Key Backup

#36

Post by G_o_D »

Plus just place punch card on paper apply a paint with brush of better spray and you printed your holes will be printed on paper share anyone (Softcopy ツ)

alternatively for fun use photographic chemical film paper and dark room, place plate on light source flash and capture holes on film

Steganography ideas Another fun-> divide cut plate into puzzle give pieces to different people only when puzzle combined reveals full datà

Another -> Have two or more plates with extraa binary bits holes and masking plates, when they are superimposed/stacked in proper order or aligment then uncessary bits will be masked revealing useful bits

Re: Show HN: PunchCard Key Backup

#38

Post by ciprian_craciun »

kristianp wrote: post #37

I enjoyed the brevity of the python snippet required for this: python -c '_secret = "d74ae47dc6f599d3f9cb847bd77d6b7c" ; print (bin(int(_secret,16))[2:])'

The only one minor issue with this snippet (which I now just realized), is that if the secret has the first few bits on zero (i.e. anything that starts with something under `7`) then the resulting bits would be less than 128, and thus the user has to copy them from right to left (the least significant one) on the card from bottom-right upward.

Alternatively, one could use the `.rjust(128,"0")` to pad the bits, as in:

python -c '_secret = "d74ae47dc6f599d3f9cb847bd77d6b7c" ; print (bin(int(_secret,16))[2:].rjust(128,"0"))'

Re: Show HN: PunchCard Key Backup

#39

Post by ciprian_craciun »

G_o_D wrote: post #36

Plus just place punch card on paper apply a paint with brush of better spray and you printed your holes will be printed on paper share anyone (Softcopy ツ) alternatively for fun use photographic chemical film paper and dark room, place plate on light source flash and capture holes on film Steganography ideas Another fun-> divide cut plate into puzzle give pieces to different people only when puzzle combined reveals fu…

With regard to the puzzle idea: if the secret is quite sensitive, and assuming you split the card in say 4 parts, then coercing 2 of them to reveal their puzzle pieces, would reduce the brute force security of the secret from 128 bits to just 64 bits, which could be easily breakable.

With regard to the superimposed cards idea: this is equivalent with an "and" operation on bits, which in terms of entropy means that having one of the cards would reduce the brute force security by the amount of "0" bits (i.e. non holes in the card), because those bits can never be "1" due to superimposing.

The only safe way one can *easily* create multiple shares is through bit-wise XOR-ing:

* generate two random number, encode them into the cards, the actual secret is the XOR of the two numbers;

* K out of N is possible (I've seen some articles / StackOverflow posts), similar (though not quite exactly) to how RAID5 handles data;

Re: Show HN: PunchCard Key Backup

#40

Post by ciprian_craciun »

ggm wrote: post #34

Numbered array from 1...

Initially the bits were counted from 0, however this had two issues:

* using 0 as starting point would immediately trigger one's "computer science" instinct, and then it's uncertain which bit is actually bit `0`? the least significant one (as is in most cases), or the most significant one?

* by using 1 as the starting point, I hope would induce most people to just use it as a counter to number things in the "normal" (for westerners) left-to-right top-to-bottom, thus encoding / decoding is more "natural";

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