A better method though still not considered crypto-strength would be to take the md5 object from the POE. Lookup how to do HMAC-MD5 (its specfied in an ietf rfc) - its 2 calls to MD5 with some extra processing. For input take the key and concaternate a string and a unique number - the number can be a number that is incremented for every use, just make it a large number so it doesn't repeat e.g. a 48bit number. HMAC-MD5 will output 128bits. For each 128bit of the message to be encrypted, run this to generate 128bits, with a different (incremented) number . Then xor the plaintext and the generated bitstring. Send to the otherside the encrypted text + the first number. The receiver can re-generate the plaintext as long as the shared secret key is known.
Theres 1 other thing, how much of a problem is it if the message is changed? An attacker can change the message inside the encryption without decrypting it. And dont expect the GPS checksum to protect the message, that can be fixed within the xor.
yes or intercepts from several transmittors and sends the data as if from each other, or changes 1 bit in the location (since its a fixed location). If its random data its easy to spot at the receiver but flipping 1 bit in the less significant places of the location or swapping transmitters location is hard to spot. (swapping you can fix by using different keys). Another attack is what happens if I record the transmitted location and replay it back later, I dont see anything to stop replay attacks.
The whole point of the replies to your original question is that there are basically two levels to cryptography. One, where you're protecting data against an unsophisticated thief where any kind of non-trivial encryption would discourage them. Two, where you're up against professional cryptographers and there's great value to decoding the information. In this case, everything you've brought up would be straightforward to break. It might take some time and some sophisticated equipment, but much less than you think.
Like I said before, if you use codes then everyone wants to know your secrets.
If you want any privacy at all, NEVER BRING A LAPTOP ON A PLANE!!!
(That is an outrageous and constitutionally illegal search and seizure policy and we should all do something about it!)
This whole thread worries me, since lives could be at stake
I agree Phil... Plus, if there was ever an application needing strong Intellectual Property (IP) protection on-chip, this is probably it. Unfortunately Propeller doesn't have any IP protection.
Here are the 20 strings I promised. Though this may be easy to crack for the NSA, I am confident that our mutual enemy will have some problems with this. I am not doing this as a response to a challenge, it was said that if it is going to be cracked then it should be done here and I agree.
Hint section:
1. This string is similar to the message shown in a previous thread.
Good luck.
E1 BE 50 E2 45 EF 11 48 B1 88 13 DE C4 84 99 CB 19 52 D4 13 B6 98 45 D7 AA F0 90 54 C6 2 A5 5 22 2
Comments
Theres 1 other thing, how much of a problem is it if the message is changed? An attacker can change the message inside the encryption without decrypting it. And dont expect the GPS checksum to protect the message, that can be fixed within the xor.
<*ek7GQ20K*31.12345*-110.12345*>
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·- Was it pin 11 or 26?· Hmmm....··I think the smell of smoke tells the whole story.· Must be 26.
Michael King
Application Engineer
R&D
Digital Technology Group
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·- Was it pin 11 or 26?· Hmmm....··I think the smell of smoke tells the whole story.· Must be 26.
Michael King
Application Engineer
R&D
Digital Technology Group
If you want any privacy at all,
NEVER BRING A LAPTOP ON A PLANE!!!
(That is an outrageous and constitutionally illegal search and seizure policy and we should all do something about it!)
I agree Phil... Plus, if there was ever an application needing strong Intellectual Property (IP) protection on-chip, this is probably it. Unfortunately Propeller doesn't have any IP protection.
David
Hint section:
1. This string is similar to the message shown in a previous thread.
Good luck.
E1 BE 50 E2 45 EF 11 48 B1 88 13 DE C4 84 99 CB 19 52 D4 13 B6 98 45 D7 AA F0 90 54 C6 2 A5 5 22 2
F4 6E F4 36 12 D3 FB 63 14 6D AF 95 75 E2 B3 38 D F6 C8 BB 7 44 84 8 44 D7 C4 70 2 E2 26 B1 1D 2F
66 DB 7E B6 F7 43 CD C5 FB 9D 59 D1 12 B5 1A F8 8A 4 F6 83 FB B7 2E F9 72 1A B6 2F 54 A6 9 48 33 E
29 54 C3 35 D1 82 8 E3 B5 47 E 4F AC 8C 57 C0 97 20 EB EA 92 A8 DB 25 5B E7 1A BB A4 58 E0 C9 1B 11
C2 4 1C 3D FC A8 9C 17 5D CC 41 BF 9 83 D4 A6 38 E7 3A 82 7A 48 AE 87 17 E0 C3 A1 94 D0 10 5C 14 2
C1 3 1B 3C FB A7 9B 16 5C CB 40 BE 8 82 D3 A5 37 E6 39 81 79 47 AD 86 16 DF C2 A0 93 CF F 5B 14 1
45 AD B9 2 79 3D B2 33 CB 14 94 DF B6 3A EF 4E A8 70 51 C6 A7 19 ED D2 91 A6 D8 26 5F E1 20 B6 17 F
E6 28 40 61 22 CC C0 3B 81 F0 65 E3 2D A7 F8 CA 5C D 5E A6 9E 6C D2 AB 3B 6 E7 C5 B8 F4 34 80 14 26
3A 35 50 2F 14 92 BD B7 4B E5 74 7D D8 3B 71 C 57 A1 7B DA A 2F 51 95 15 60 F8 41 D7 14 F8 77 5 3C
51 15 5E B3 33 48 DF 9C 21 F4 F1 B7 AF ED 2D 6E EC 27 C4 A5 77 EC CF 9 AA 68 DA 1E D5 20 C 89 24 18
5D DE DC FD 3 35 B9 13 CA 1D 3 8B 2 4 7D 3 BA 34 FD 6F 1F BA 32 51 92 F1 45 DE 2B 73 2F 99 38 F
86 5 A7 E1 9C C8 3E 1C 1A 95 15 D4 49 20 A4 38 D2 4F 70 B0 29 5E F6 41 A8 64 AF FB 1F 3A 6C F0 3D 29
6B B 96 93 77 28 EE 26 49 8D 8 59 F2 4B D1 6 D8 64 19 5A BA 97 79 E0 CE 3D 12 F3 CB C6 6 4D 13 33
62 CA D6 1F 96 5A CF 50 E8 31 B1 FC D3 57 E 6B C5 8D 6E E3 C4 36 C EF AE C3 F5 43 7C FE 3D D3 17 2C
B7 19 95 80 90 9C 7 F3 AC 24 F3 7B E B6 25 42 A0 E9 33 D8 7 62 3D 86 D1 F3 18 5C CF 22 A6 A 1 2
59 CE 71 A9 EA 36 C0 B8 EE 90 4C C4 5 A8 D EB 7D F5 E9 76 EE AA 21 EC 65 D A9 22 47 99 FA 3B 33 1
5 42 CB 2D 33 61 4 E4 8 2B 57 DE 38 B4 1B B1 E4 B6 44 11 34 AF 78 5B C7 98 1D F0 DB AD A0 D9 12 14
44 BF E2 E1 85 D0 91 D5 A1 7E F1 C0 44 FB FC D8 CF B 4B 88 6 44 E2 D1 96 10 EE 28 C2 8E 16 45 20 3A
D6 1D 3E E5 84 ED E 52 E6 C4 6 9E 5F ED 13 CA 1D FB 89 F9 1 7D 2 B7 4E F9 87 1D BD 36 67 A2 31 F
1A AC C2 E0 96 D3 47 43 DF 58 8F D5 1B 61 6 51 99 75 B8 4 26 4C 8F 2 72 F6 3B D3 10 DA 66 28 6 37
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·- Was it pin 11 or 26?· Hmmm....··I think the smell of smoke tells the whole story.· Must be 26.
Michael King
Application Engineer
R&D
Digital Technology Group
Post Edited (Sniper King) : 8/4/2008 7:39:53 PM GMT