Description
Convolutional codes are frequently used in wireless communication standards: in mobile networks, in Wi-Fi, but also in space transmissions.
With a convolutional code, a message m(x) is multiplied bit by bit by two defined polynomials p1(x) and p2(x).
For example, in GSM (also called second generation mobile network, 2G), two outputs are calculated: c1(x) = m(x) * p1(x) and c2(x) = m(x) * p2(x).
The transmitted message alternately contains the bits of c1(x) and c2(x).
Here, you have a flag encoded by the polynomials G0 = X^4 + X^3 + 1 and G1 = X^4 + X^3 + X + 1 defined in the GSM standard. Will you be able to recover the flag?
Files
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convolu-quoi.go
2.02 KiB – 759d3fa0581faffeb71cddd4f36be589180a50ef193672ba849e45de33d51b10
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