Energy consumption by mobile or sensor node when executing xor / encryption / decryption I try to estimate the energy consumption by a sensor node when executing an authentication algorithm witch contains operations (hashing, XOR, Encryption / decryption by public/private key, addition,...). 

The algorithm is named MDA (Message Digest Based Authentication). It contains:

(SN:sensor node; CH: cluster head; Th: hash operation ; Tx: transmit;
 Touex: XOR; Trec: reception; Tenc: encryption; Tdec: decryption)
**-Registration Phase :** 
*SN--&gt;CH:
2Th+Tx+Touex
*CH--&gt;SN:
Trec+Touex+3Th+Tenc+Tx
**- Authentication Phase :**
*SN--&gt;Ch
Th+2Tenc+Tx
*CH--&gt;SN
Trec+Touex+2Tdec+Th
**- Numeric Certif**
*CH--&gt;SN
Th+Tenc+Tx
*SN:
Trec+Tdec


So I ask if there are measurements that I can use to calculate energy.
There's a degree of electronics twiddling necessary for this.  You start with:-



A stiff power supply passing through a shunt resistor is typically used, which is then monitored with a storage oscilloscope. A low resistance is necessary, say 0.1 Ohms, but that really depends on the operating point consumption of your sensor device. You can't have the power supply dipping below operational thresholds as that will nullify the experiment.  Control the device to perform your required operations, and you'll read a voltage off the scope.  Then simply $consumption = \frac{voltage}{resistance}$.

This is called power analysis, and Wiki has an entry level article. You'll see from the graphic on the RHS that the power signature is not really as simple as I implied.  That's where a lot of statistics and probability matching will become necessary.  Some don't even bother with power consumption (amps) calculations and go with purely graphical approaches.  A wibbly waveform might indicate a correct key, and a wobbly waveform might indicate a bad key. This part is entirely characteristic of the individual device under test. And how you intend to exactly distinguish various cryptographic operations within the sensors.

Also one of the challenges will be in managing to grab and isolate the power consumption at the point of cryptographic operation, rather than simply running the status LEDs. You may need additional wiring between the control inputs and the oscilloscope's trigger input.

But it's a start...