A common approach of system identification and machine learning is to
generate a model by using training data to predict the test data instances as
accurate as possible. Nonetheless, concerns about data privacy are increasingly
raised, but not always addressed. We present a secure protocol for learning a
linear model relying on recently described technique called real number secret
sharing. We take as our starting point the PAC Bayesian bounds and deduce a
closed form for the model parameters which depends on the data and the prior
from the PAC Bayesian bounds. To obtain the model parameters one needs to solve
a linear system. However, we consider the situation where several parties hold
different data instances and they are not willing to give up the privacy of the
data. Hence, we suggest to use real number secret sharing and multiparty
computation to share the data and solve the linear regression in a secure way
without violating the privacy of data. We suggest two methods; a secure inverse
method and a secure Gaussian elimination method, and compare these methods at
the end. The benefit of using secret sharing directly on real numbers is
reflected in the simplicity of the protocols and the number of rounds needed.
However, this comes with the drawback that a share might leak a small amount of
information, but in our analysis we argue that the leakage is small.