The property that linearly homomorphic signature (LHS) enables linear computation on signed data makes this primitive commonly used to secure the network coding based application against pollution attacks. The security of LHS wholly depends on the security of secret signing keys; once a secret key is compromised, the application system’ security will be broken. However, as relatively insecure mobile devices are increasingly used in network coding application systems, the key exposure issue is becoming more prevalent. On the other hand, with the quantum technology development, some existing LHS schemes based on some traditional number-theoretic primitives are susceptible to quantum cryptanalysis. Hence, facing the dual threats of the exposure of secret keys in reality and the future effiffifficient quantum computers, we integrate forward security into LHS, and present a forward-secure identity-based LHS scheme (FSIBLHS) based on lattice assumptions, which achieves post-quantum security, and even if the current secret key is compromised, the validity of signatures of previous time periods is still guaranteed. We defifine the fifirst security model on forward security of LHS, and prove that the proposed scheme can resist adaptively chosen identity and datasets attack under lattice assumption. Moreover, compared with previous related works, the performance analysis shows that our scheme enjoys a comparable computation cost and has a lower communication cost, and provides higher security and stronger functionality.