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I have a pair of AVR's that communicate over the 2.4GHz link using NRF24l01+. The payload sent is 5 bytes long.

Right now the payload sent is in clear format so that anyone with enough knowledge and skill could theoretically build a device to intercept the data stream.

Can you please provide me with some recommendations on ways to encrypt this data stream considering it would be implemented on a 8 bit AVR (small code size) and would be done real time (so should be fast).

Thanks!

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XXTEA, Keeloq, TEA are suitable encryption algorithms for microcontrollers with small amount of RAM.

If the data are usually constant you will have to use a rolling code method to prevent replay attack.

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  • \$\begingroup\$ Decided to go with XTEA with 1 byte random data inserted to randomize the encrypted output when using the same input data \$\endgroup\$
    – Ankit
    Commented Mar 2, 2015 at 20:19

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