X3 C is a Swedish company which develops a world wide good tracking system by using ARFID

tags placed on every item which has to be delivered and base stations as gateway in a wireless

sensor network. The requirement of a long lifespan of their ARFID tags made it difficult to

implement security. Firstly an evaluation of possible security mechanisms and their power

consumption was done by measuring the avalanche effect and character frequency of the sym-

metric algorithms Blowfish, RC2 and XTEA. Secondly, the required CPU time which is needed

by each algorithm for encrypting a demo plaintext, was measured and analyzed. Summariz-

ing both analysis, the XTEA algorithm, run in CBC mode, is the recommendation for the XC

ARFID tags. The testing processes and the results are presented in detail in this thesis.