  The popularity of smartphones has led to the growth of mobile app markets,
creating a need for enhanced transparency, global access, and secure
downloading. This paper introduces AGChain, a blockchain-based gateway that
enables trustworthy app delegation within existing markets. AGChain ensures
that markets can continue providing services while users benefit from
permanent, distributed, and secure app delegation. During its development, we
address two key challenges: significantly reducing smart contract gas costs and
enabling fully distributed IPFS-based file storage. Additionally, we tackle
three system issues related to security and sustainability. We have implemented
a prototype of AGChain on Ethereum and Polygon blockchains, achieving effective
security and decentralization with a minimal gas cost of around 0.002 USD per
app upload (no cost for app download). The system also exhibits reasonable
performance with an average overhead of 12%.
