output tag w 24 form the data transmitted through the communication channels or stored on a storage media with the signing of each plaintext string the current value of the counter ctr is incremented or otherwise changed to a new value at 76 fig1 shows an example in which the counter is incremented by one the incremented value of the counter is used in the signing of the input plaintext string of the next message fig1 represents the verification of a plaintext string x 23 using counter ctr 72 and the input authentication tag w u2032 25 first the counter ctr 72 is compared at 78 with constant q s representing the maximum number of messages that can be signed if the comparison ctr u2266 q s fails then the input plaintext string x 23 is rejected if ctr u2266 q s then the output of the logical u201c and u201d operators 88 applied to the counter ctr 72 the first random initial first random initial vector y 0 81 the second random initial vector y 0 85 and the plaintext blocks x 1 x n 21 are submitted to the signing function 68 using a single secret key k 31 resulting in the computed tag w 24 the computed tag w 24.