Multi-party learning is an indispensable technique for improving the learning
performance via integrating data from multiple parties. Unfortunately, directly
integrating multi-party data would not meet the privacy preserving
requirements. Therefore, Privacy-Preserving Machine Learning (PPML) becomes a
key research task in multi-party learning. In this paper, we present a new PPML
method based on secure multi-party interactive protocol, namely Multi-party
Secure Broad Learning System (MSBLS), and derive security analysis of the
method. The existing PPML methods generally cannot simultaneously meet multiple
requirements such as security, accuracy, efficiency and application scope, but
MSBLS achieves satisfactory results in these aspects. It uses interactive
protocol and random mapping to generate the mapped features of data, and then
uses efficient broad learning to train neural network classifier. This is the
first privacy computing method that combines secure multi-party computing and
neural network. Theoretically, this method can ensure that the accuracy of the
model will not be reduced due to encryption, and the calculation speed is very
fast. We verify this conclusion on three classical datasets.