> For the complete documentation index, see [llms.txt](https://fogcomputingchain.gitbook.io/fog-computing-chain/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://fogcomputingchain.gitbook.io/fog-computing-chain/key-technology/cross-chain/backbone-to-side-chain-transfer.md).

# Backbone to side chain transfer

The transfer of the FOGR backbone to the side chain is based on SPV. The integrated SPV module on the side chain is required to synchronize the backbone block and the transfer transactions of the backbone to the side chain on the backbone at any time.The transfer process is as follows:

🔵1. The user transfers n FOGR, to the backbone from the address U to the address S represe n ting the side chain on the backbone and sends it to the transaction with its own address u, in the side chain, and this transaction is marked as ab1.

🔵2. The miner node of the backbone packages the ab1 and successfully.

🔵3. After waiting for enough confirmation, the SPV module of the rotating arbitrator node A obtains the transfer transaction on the main chain, obtains the transfer address U from the transaction, and constructs the transaction AB2 for issuing the token to U. The number of issuing token is equal to the number of transfer from U to S in AB1, and AB2 also carries SPV Prove path and AB1.

🔵4. The rotating arbitrator node A sends the ab2 to the side chain node. Side chains package the ab2 out of the blocks. After waiting for eno u gh co n firmation, the user recorded n FOGR. s with his side chain address u that he saw on the wallet.


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