1. A method for iris recognition, comprising the steps of: establishing a data processing sub-system in an iris recognition system configured to perform iris recognition through the steps of: performing a training stage of operation in said iris recognition system, including the steps of: (a) acquiring a plurality of training iris samples ={θ 1 , θ 2 ,. .. , θ N } with a plurality of different sensors {S 1 , S 2 ,. .. , S Ns } for a plurality of subjects {y 1 , y 2 ,. .. y Nc }, (b) for each pair θ i ,θ j of training iris samples from said plurality thereof, computing, by said data processing sub-system of said iris recognition system, a similarity measure (θ i ,θ j ) between said training iris samples θ i and θ j , where θ i , θ j ε , (c) forming, by said data processing sub-system, an initial training kernel matrix 0 = (θ i ,θ j ) for said plurality of training iris samples, (d) iteratively updating, by said data processing sub-system, said initial training kernel matrix 0 by applying Bregman projections at each iteration, thereby forming a final training kernel matrix A (θ i ,θ j ), and thereby establishing a space of allowable transformations for said training iris samples θ i ,θ j satisfying predetermined constraints {θ i ,θ j } imposed between said training iris samples θ i and θ j , (e) extracting adaptation parameters σ ij through processing said initial and final training kernel matrices by said data processing sub-system; performing a testing stage of operation subsequently to said training stage of operation through the steps of: (f) acquiring a test iris sample θ t , (g) computing, by said data processing sub-system, said similarity measure (θ t ,θ) for said testing iris sample θ t and said plurality of the training iris samples θε , (h) forming, by said data processing sub-system, an initial test matrix 0 test = (θ t ,θ), (i) computing, by said data processing sub-system, a test adapted kernel function A test for said test iris sample θ t based on said initial test matrix 0 test and said adaptation parameters σ ij as A ⁢ ( θ t , θ ) = ⁢ ( θ t , θ ) + ∑ ij ⁢ σ ij ⁢ ⁢ ( θ t , θ i ) ⁢ ⁢ ( θ j , θ ) ; and performing a matching routine subsequently to said testing stage of operation through the steps of: (j) computing, by said data processing sub-system, a distance measure between said test iris sample θ t and an enrollment iris sample θ en , and (k) verifying, by said data processing sub-system, said test iris sample as genuine if said distance measure in said transformed space between said test and enrollment iris samples is smaller than a predetermined threshold.