We propose a proxy signcryption scheme for a multi-party setting, resistant to randomness leakage and setup attacks. Our scheme is an alternative to typical constructions, based on a double Schnorr signature approach, where the linear combination of long term secrets and ephemeral random values occurs both at the initiator and proxy nodes. Our scheme is provably secure in a new stronger model, where the adversary can control the randomness of both parties. Moreover, our proposition is well suited for networks of many independent and moving nodes; especially modern railway infrastructure and vehicle-to-vehicle/infrastructure (V2X) environments, where a broad range of devices with potentially weak computational power and inadequate randomness, is used. Early benchmarks and performance analysis from our proof of concept implementation, suggest that nodes, which use regular Schnorr based schemes, could be successfully upgraded to our more secure alternative construction. Collected timings are still at the acceptable level, proving the applicability of our scheme in modern railway and V2X environments.