Note: All articles published on Edgecase Datafeed are datafeed articles and are signed by Edgecase Datafeed. A datafeed article may contain an article, a signed article, or a checkpoint article. To verify a datafeed article means to check that the GPG digital signature attached to it is mathematically valid and optionally to check its time of publication as measured by block height on the bitcoin blockchain. The most recent articles may not yet have been published on the bitcoin blockchain.
1) Install GPG 1.4.x (preferably 1.4.10), if you don't already have it on your system. How to do this is beyond the scope of this recipe.
2) Check that your system has a utility for calculating the SHA256 hash of a file. If it does not, find and install one. How to do this is beyond the scope of this recipe.
3) Browse to the checkpoint article that you wish to verify. In the Downloads menu, there should be a "Download this article" link to the original datafeed article, which is a text file. Clicking this link should cause your browser to ask you to download this text file.
4) Follow this recipe How to verify a datafeed article to verify the Edgecase Datafeed signature on the checkpoint article.
5) Open a commandline terminal, change directory to the directory that contains the original datafeed article file, and run the following command to find its SHA256 hash. Replace "sha256" with the appropriate command on your system. Replace "2017-06-28_edgecase_datafeed_article_0_checkpoint_0.txt" with the filename of the checkpoint you are verifying.
$ sha256 2017-06-28_edgecase_datafeed_article_0_checkpoint_0.txt
6) Taking this SHA256 hash as a bitcoin private key, use a bitcoin utility to find the corresponding bitcoin address. For example, you could browse to www.bitaddress.org, click Wallet Details, paste the SHA256 hash into the "Enter Private Key" box, and click View Details.
The bitcoin address found from this SHA256 hash:
7) Look up this bitcoin address on a bitcoin node that you can access. For example, you could browse to http://blockchain.info and paste this address into the search box. Find the earliest transaction. Click the transaction id of this transaction, which in this example will be b2f093a08e80f281889bc19b1ae441d3ead93cd10e58c640202916beb25d1670. In the Summary for this transaction, you should find an entry entitled "Included in Blocks", which should have a value similar to: 473266 ( 2017-06-28 17:28:22 + 7 minutes ). You now know that the earliest transaction to this bitcoin address occurred in this block (473266), which was mined at this approximate time and date.
8) You have now confirmed that this checkpoint article was published by Edgecase Datafeed at a specific time and has not been changed since that time.
Time is measured here as block height on the bitcoin blockchain.
An original, unaltered copy of this checkpoint article is now in your possession.