In my previous work several important concepts like template, contract and transaction about DAML were introduced, with a very simple IOU demonstrating the relationship between them. We have seen how a new contract instance of the same template is created through choices. Here we make it more interesting and realistic: how two contracts are interacting with each other in DAML through choices.

DAML tutorial 6 gives us a good example, which is good for extending our previous IOU example. As it is needed to make owner as signatory (in addition to issuer), the transfer of IOU now is implemented as proposal-acceptance model, which means that one party proposes a transfer, and the other party can accept or reject it. …


Early this July my article System Channel and Application Channel was about a tutorial “Adding an Org to a Channel” (link), driven by a question from my readers. I received another question this week which again led me to revisit this topic. The question was about modifying a batch timeout (amount of time to wait before creating a block) in Hyperledger Fabric. While it is quite clear that we can update configuration through the standard (and tedious) process, what puzzled me at the beginning is which channel I should work on: system channel or application channel.

My very first guess is that, as blocks are created in an orderer, the configuration update should be made on the system (orderer) channel, and then the orderer will honour this new timeout for all channels. After some experiments my guess is wrong! (Always learn new things in each hands-on practice.) …


This is another rework on my recent article. The source is a tutorial of Fabric CA in Hyperledger Fabric documentation. The tutorial was done with version 1.4, and my first work done early this July was also made on the same version. Since then I keep receiving queries to make it running in v2.0, as there are many changes from v1.4 to v2.0 and the commands are not used directly in v2.0. As a result I rewrite this companion guide to make it workable in v2.2.

We follow the same network design and setup. Unlike the previous work, we consolidate the four scripts in our previous work into one, bringing up all the CA and registering all the entities. No CLI containers are needed as we are using binary peer directly in the localhost. …


KC Tam

Happy to share what I learn on blockchain. Visit http://www.ledgertech.biz/kcarticles.html for my works. or reach me on https://www.linkedin.com/in/ktam1/.

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