I'm reading through this Github Repo from Blockcerts.org on how to issue digital certificates on the bitcoin blockchain.

What is confusing me is whether or not each issuing each digital certificate in this manner costs money.

On one hand, I've read through the high-level Blockcerts documentation and blogs and haven't seen any reference to financial costs to issuing certificates on the bitcoin blockchain.

On the other hand, in the cert-issuer repo it notes in the "Transaction Structure" of "How Batch Issuing Works", the issuer needs a minimal amount of Bitcoin to create the transaction. At the very least, this is a fixed cost.

Additionally, in the documentation we see:

Ensure you've transfered a small amount of coin to your issuing address. Note that each certificate costs 12750 satoshi


Make sure you have enough BTC in your issuing address. ($0.08 USD)

So, it sounds like each certificate costs about $0.30 to issue? Just want to make sure I understand correctly.

(Please note, I am totally new to blockchain, so apologies if this is a dumb/obvious question).

  • link for documentation is not working anymore Apr 22, 2019 at 23:52

2 Answers 2


(I'm a Blockcerts developer)

Andrew is right -- that is simply the transaction fee. That fee is the same no matter the number of certificates in the batch for Blockcerts issuing.

I note that the documentation you're referring to is out of date, so I updated it just now to add more current fee information and to clarify how to determine the transaction fee.


  • Ensure you've transferred sufficient funds to your issuing address to cover the transaction fee.
    • The transaction fee is the same no matter the number of certificates in the batch.
    • The default transaction fee used by cert-issuer is 60,000 satoshis (~$1.50 USD, 7/3/2017).
    • Because the transaction fee is a factor in confirmation time, you may decide to increase or decrease this value in the config file (read more about current transaction fee/latency estimates: https://bitcoinfees.21.co/).

The project you are looking at uses a Bitcoin transaction to commit something to the blockchain (because that's the only way to use the blockchain, with a transaction). This transaction must pay a transaction fee, just like every other Bitcoin transaction. So when you issue a certificate (or whatever) and you make a transaction for it, your transaction must pay a transaction fee otherwise it will take a long time to be included in the blockchain.

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