# Uni Directional Payment

**URL:** <https://forum.soliditylang.org/t/uni-directional-payment/1067>\
**Category:** Documentation\
**Created:** [June 15, 2022, 3:10am UTC](https://forum.soliditylang.org/t/uni-directional-payment/1067 "2022-06-15T03:10:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![porscheTan](https://avatars.discourse-cdn.com/v4/letter/p/eada6e/32.png) [@porscheTan](https://forum.soliditylang.org/u/porscheTan)\
**Post date:** [June 15, 2022, 3:10am UTC](https://forum.soliditylang.org/t/uni-directional-payment/1067/1 "2022-06-15T03:10:17Z")

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Dear All Smart Contract Developers,

I am an amateur in this space and would greatly appreciate your help in helping me understand certain concepts from this documentation (Uni-Directional Payment Channel).

In this documentation, it states that "`Alice` authorizes a payment by signing a message (off chain) and sends the signature to `Bob`". I am unsure what it means by signing a message (off chain) in this case, is there a function I am supposed to create or what am I supposed to do?

I sincerely apologise for my inept in this field!

Regards,  
Porsche Tan

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**Author:** ![czepluch](https://sea1.discourse-cdn.com/flex001/user_avatar/forum.soliditylang.org/czepluch/32/1874_2.png) [@czepluch](https://forum.soliditylang.org/u/czepluch)\
**Post date:** [June 15, 2022, 5:21pm UTC](https://forum.soliditylang.org/t/uni-directional-payment/1067/2 "2022-06-15T17:21:04Z")

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It most likely means that Alice uses her private key to sign a message to Bob that says that she commits to performing this transaction on chain at some point in the future if Bob wants to settle. I am not sure which project you’re reading the documentation from, but at least in the case of Raiden this is pretty much how it works. The parties involved in a channel exchange messages off-chain that can later be understood by a smart contract on-chain in order to settle the balances in the channel.