  Different transforms used in binding a secret key to correlated
physical-identifier outputs are compared. Decorrelation efficiency is the
metric used to determine transforms that give highly-uncorrelated outputs.
Scalar quantizers are applied to transform outputs to extract uniformly
distributed bit sequences to which secret keys are bound. A set of transforms
that perform well in terms of the decorrelation efficiency is applied to ring
oscillator (RO) outputs to improve the uniqueness and reliability of extracted
bit sequences, to reduce the hardware area and information leakage about the
key and RO outputs, and to maximize the secret-key length. Low-complexity
error-correction codes are proposed to illustrate two complete key-binding
systems with perfect secrecy, and better secret-key and privacy-leakage rates
than existing methods. A reference hardware implementation is also provided to
demonstrate that the transform-coding approach occupies a small hardware area.
