Threshold signature scheme with multiple signing policies

Based on one cryptographic assumption, a basic threshold scheme is derived which allows a group of users to share multiple secrets. The major advantage of the threshold scheme is that only one secret shadow needs to be kept by each user. The basic threshold scheme is applied to design an efficient threshold signature scheme with multiple signing policies. The threshold signature scheme with multiple signing policies allows multiple secret keys to be shared among a group of users, and each secret key has its specific threshold value. Different secret keys can be used to sign documents depending on the significance of the documents. Once the number of co-operated users is greater than or equal to the threshold value of the group secret key, then they can co-operate to create group signatures. Similarly, each user keeps only one secret shadow.