Step 1: Requesting a digest in QLDB

To request a digest (console)

1. Sign in to the AWS Management Console, and open the Amazon QLDB console at https://console.aws.amazon.com/qldb.

2. In the navigation pane, choose Ledgers.

3. In the list of ledgers, select the ledger name for which you want to request a digest.

4. Choose Get digest. The Get digest dialog box displays the following digest details:

   • Digest – The SHA-256 hash value of the digest that you requested.

   • Digest tip address – The latest block location in the journal covered by the digest that you requested. An address has the following two fields:

     • strandId – The unique ID of the journal strand that contains the block.

     • sequenceNo – The index number that specifies the location of the block within the strand.

   • Ledger – The ledger name for which you requested a digest.

   • Date – The timestamp when you requested the digest.

5. Review the digest information. Then choose Save. You can keep the default file name, or enter a new name.

   Note

   You might notice that your digest hash and tip address values change even when you don't modify any data in your ledger. This is because the console retrieves the ledger's system catalog each time that you run a query in the PartiQL editor. This is a read transaction that gets committed to the journal and causes the latest block address to change.

   This step saves a plaintext file with contents in Amazon Ion format. The file has a file name extension of .ion.txt and contains all the digest information that was listed on the preceding dialog box. The following is an example of a digest file's contents. The order of the fields can vary depending on your browser.

   {
     "digest": "42zaJOfV8iGutVGNaIuzQWhD5Xb/5B9lScHnvxPXm9E=",
     "digestTipAddress": "{strandId:\"BlFTjlSXze9BIh1KOszcE3\",sequenceNo:73}",
     "ledger": "my-ledger",
     "date": "2019-04-17T16:57:26.749Z"
   }

6. Save this file where you can access it in the future. Later, you can use this file to verify a document revision against.

   Important

   The document revision that you verify later must be covered by the digest that you saved. That is, the sequence number of the document's address must be less than or equal to the sequence number of the Digest tip address.