In this paper we propose a general biometric cryptosystem framework inspired by the code-offset sketch. Specifically, the properties of digital modulation and turbo codes with soft-decoding are exploited to design a template protection system able to guarantee high performance in terms of both verification rates and security, also when dealing with biometrics characterized by a high intra-class variability. The effectiveness of the presented approach is evaluated by its application as case study to on-line signature recognition.

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In this paper a secure Incremental Redundancy - Hybrid Automatic Repeat Request (IR-HARQ) scheme, based on Turbo Codes (TC), is proposed. Typical drawbacks of HARQ systems, such as spectral efficiency, latency unpredictability, correct packet delivery control (under fixed dead-line time) are definitively minimized thanks to a mathematical approach that exploits the statistical property of Additive Gaussian White Noise (AWGN) and the theoretical evaluation of Turbo Codes performance (in terms of symbol and codeword error probability). In order to decide if the received frame is correct and authentic, or a NACK (Non ACKnowledgment) packet must be forwarded to the sender, the codeword is examined through a verification test based on an adaptive threshold that: 1) depends on channel condition; 2) takes into account the error probability associated with of the current re-transmission step turbo code redundancy amount; 3) verifies if the sender is authentic (i.e. if he/she makes use of the correct turbo encoding parameters)

In this paper we propose an Orthogonal Frequency Division Multiplexing Ultra Wide Band (OFDM-UWB) system that introduces encryption, mutual authentication, and data integrity functions, at the physical layer, without impairing spectral efficiency. Encryption is performed by rotating the constellation employed in each band by means of a pseudorandom phase-hopping sequence. Authentication and data integrity, based on encrypted-hash, are directly coupled with Forward Error Correction (FEC). Dependence of the phase hopping sequence on the transmitted message deny the use of the phase hopping obtained by means of known and chosen plaintext attacks for decryption of further messages.Moreover, since phase hopping generation keys change very rapidly they are also difficultly detectable from a hypothetic man in the middle. Computer simulations confirm the superior performance, even in terms of BER, to a standard PSK-OFDM system, due to the FEC capabilities of encrypted hash.

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