A method for uniquely identifying and authenticating at least one user by means of at least one personalized identifier, the method comprising: during registration of the at least one user: storing, by a processor, a first set of records associated with the at least one user, each record comprising a text, a golden copy of biometric templates and a model associated with the golden copy of biometric templates, wherein the text, the golden copy of biometric templates and the model are associated with the at least one personalized identifier; assigning, by the processor, at least one privilege level to the at least one personalized identifier in the each record of the first set of records based on one or more attributes; during identification and authentication of the at least one user: capturing, by the processor, the at least one personalized identifier in the form of a biometric sample, wherein the biometric sample is in the form of speech or a handwriting signature; converting, by the processor, the biometric sample into one or more text-scripts; retrieving, by the processor, a second set of records from the first set of records by matching the one or more text-scripts with the stored text in each record of the first set of records and accordingly identify a model set comprising one or more models associated with each record from the second set of records; comparing, by the processor, a biometric template corresponding to the biometric sample with the golden copy of biometric templates of each of the record from the second set of records to generate a matching score, wherein the matching score is generated for each model in the model set; when the number of models in the model set having the matching score greater than or equal to a pre-defined threshold score is one: identifying, by the processor, the user uniquely using the model from the model set having the matching score greater than or equal to a pre-defined threshold; when the number of models in the model set having the matching score greater than or equal to a pre-defined threshold score is more than one: prompting, by the processor, the user to provide a real-time biometric sample corresponding to a randomly generated text displayed to the user, wherein the real-time biometric sample is in the form of speech or a handwriting signature; comparing, by the processor, a biometric template corresponding to the real-time biometric sample with the golden copy of biometric templates associated with the models from the model set, having the matching score greater than or equal to a pre-defined threshold score to uniquely identify the user; and re-calibrating, by the processor, the model set having the matching score greater than or equal to a pre-defined threshold score using the biometric template corresponding to the real-time captured biometric sample. during registration of the at least one user: storing, by a processor, a first set of records associated with the at least one user, each record comprising a text, a golden copy of biometric templates and a model associated with the golden copy of biometric templates, wherein the text, the golden copy of biometric templates and the model are associated with the at least one personalized identifier; assigning, by the processor, at least one privilege level to the at least one personalized identifier in the each record of the first set of records based on one or more attributes; during identification and authentication of the at least one user: capturing, by the processor, the at least one personalized identifier in the form of a biometric sample, wherein the biometric sample is in the form of speech or a handwriting signature; converting, by the processor, the biometric sample into one or more text-scripts; retrieving, by the processor, a second set of records from the first set of records by matching the one or more text-scripts with the stored text in each record of the first set of records and accordingly identify a model set comprising one or more models associated with each record from the second set of records; comparing, by the processor, a biometric template corresponding to the biometric sample with the golden copy of biometric templates of each of the record from the second set of records to generate a matching score, wherein the matching score is generated for each model in the model set; when the number of models in the model set having the matching score greater than or equal to a pre-defined threshold score is one: identifying, by the processor, the user uniquely using the model from the model set having the matching score greater than or equal to a pre-defined threshold; when the number of models in the model set having the matching score greater than or equal to a pre-defined threshold score is more than one: prompting, by the processor, the user to provide a real-time biometric sample corresponding to a randomly generated text displayed to the user, wherein the real-time biometric sample is in the form of speech or a handwriting signature; comparing, by the processor, a biometric template corresponding to the real-time biometric sample with the golden copy of biometric templates associated with the models from the model set, having the matching score greater than or equal to a pre-defined threshold score to uniquely identify the user; and re-calibrating, by the processor, the model set having the matching score greater than or equal to a pre-defined threshold score using the biometric template corresponding to the real-time captured biometric sample.