Introduction to Forward-Secure Digital Signature Scheme Project:

This paper discussed about “forward security” , that is a security approach which ensures using secrets for short time periods and also reduces the damage when the secrets are exposed. This paper also describes how to design a forward-secure signature scheme.


In a forward-secure signature scheme, if the current secret key is compromised, signatures from past time periods can still be trusted. A forward-secure digital signature scheme is a key-evolving digital signature scheme. Like a standard signature scheme, a key-evolving digital signature scheme contains algorithms related to key generation, signing and verification. Throughout the lifetime of this scheme, the public key remains unchanged. In this scheme, operations are divided into certain time periods and each period uses a different secret key to sign a message.

A public update algorithm in this scheme is used to computes the secret key for the new time period based on the previous period. But in this scheme we can able to get the secret key for the current period but not able to get any previously used secret keys. So, in order to overcome this drawback a forward-secure signature scheme comes into picture.
The public key for the forward-secure scheme is located at the root of the tree. In order to sign a message in a certain time period there is a need to use the secret key of the corresponding leaf and attach to the signature a certification chain depends on the root path to that leaf.  In this scheme nodes are created dynamically to maintain forward security. 

Transformation form secure identification scheme into a secure signature scheme without depends on random oracles is based on the concept of authentication trees.      Forward-secure signature scheme is designed by not relying on random oracles.  In this scheme whole tree nodes are created dynamically similar to that of GMR scheme.

The resulting scheme needs to remember previous message signature to compute the next signature. The length of each signature grows along with the signed messages. The main advantage of Forward-Secure Digital Signature Scheme is that we can obtain a signature scheme which is forward secured based on the security of the corresponding identification scheme.