Systems and methods are provided for encoding and decoding data (such as, for example, an encryption key) using a physiological signal. A data item string is separated into a defined number of component segments and each component segment is used as a coefficient of a polynomial equation. A plurality of signal features are then identified from a physiological signal and a plurality of ordered pairs are created based on the plurality of identified signal features using the polynomial equation. A data package including the plurality of ordered pairs and obfuscated by a plurality of chaff points is transmitted to another system. The receiver system uses a corresponding physiological signal to filter out the chaff points and to reconstruct the polynomial equation, for example, by LaGrangian interpolation. The coefficients of the reconstructed polynomial equation are then used to derive the encoded data item string.