in all the subsequent ptk frames exchanged for that current ptk creation procedure accordingly all related ptk frames have the same ptk index in one embodiment if no ptk was previously created between the initiator and responder then ptk index field 304 is set to u201c 0 u201d otherwise ptk index field 304 is set to the value of u201c 1 u201d minus the ptk index field value last used to successfully create a ptk between the two devices e g ptk index 1 u2212 ptk index last accordingly ptk index field 304 takes on a value of either u201c 0 u201d or u201c 1 u201d sender nonce field 305 is set to a statistically unique number per sender per ptk creation procedure in one embodiment in the first and second ptk frames of the current ptk creation procedure sender nonce 305 is set afresh and independently by the respective sender to an integer randomly drawn with a uniform distribution over the interval 0 2 128 in the third ptk frame of the procedure sender nonce 305 is set to the value contained in the first ptk frame initiator 601 and responder 602 independently generate a new 128 bit cryptographic random number nonce_i and nonce_r respectively as their sender nonce to use in the ptk creation procedure ptk_kmac field 306 is set to a key message authentication code kmac that is computed with certain fields of.