This paper presents a scheme for joint signing/verifying a message by many signers to provide data authenticity, integrity, and non-repudiation for a group of people. The signature security is based on the computational intractability of the discrete logarithm problem (DLP) in prime order subgroup of Z*p as in Digital Signature Algorithm (DSA) scheme. The proposed scheme is an extension of DSA to a group of signers who jointly sign the message. The Signature of a message can be verified individually for each signer, or collectively for a subgroup or entire group. Moreover, the scheme can be used for group membership authentication. Finally, the proposed scheme can be used in many applications, such as E-commerce and E-government.