7

I'm converting IPFS multi hash to hex, and after throwing away its prefix I want to attach that hash to a stellar transaction (something like here). I build it this way:

let transaction = new StellarSdk.TransactionBuilder(account)
    .addOperation(StellarSdk.Operation.payment({
        destination: supply,
        asset: StellarSdk.Asset.native(),
        amount: MIN,
    }))
    .addMemo(StellarSdk.Memo.hash(hash))
    .build();
transaction.sign(pair);

At runtime let's say the hash value is:

8c339e15bd89e7f8c7d6c754b8016a202bba12a8cdb4aabe39c6c9e30507a8f3

But after consensus has been reached, I retrieve the same transaction and it shows a different value for the memo hash:

memo: "jDOeFb2J5/jH1sdUuAFqICu6EqjNtKq+OcbJ4wUHqPM="
memo_type: "hash"

Why?

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11

While I'm not sure why this happens, this is not a different hash, its just encoded in base64

   >>> import base64
   >>> base64.b64decode('jDOeFb2J5/jH1sdUuAFqICu6EqjNtKq+OcbJ4wUHqPM=').hex()
   '8c339e15bd89e7f8c7d6c754b8016a202bba12a8cdb4aabe39c6c9e30507a8f3'
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  • I'm doing it like this bs58.decode(multiHash).slice(2).toString('hex'); and get the hex string, this is strange
    – Maxim Gaina
    Commented Jul 21, 2018 at 17:05
  • Base64 encoding is what is used to store the data on the blockchain as it is more compact. In most cases, in js-stellar-sdk, the values are stored as buffer. You can get back to hex using something like buffer.toString('hex')
    – Mister Ticot
    Commented Jul 21, 2018 at 18:40
  • 1
    @MisterTicot What's stored on the blockchain is the actual 256-bit binary string. Base64 encoding is just used as a representation to get printable characters.
    – Johan Stén
    Commented Jul 22, 2018 at 1:36
  • 3
    Ok after retrieving the memo hash it is sufficient to do this let buffer = Buffer.from(txs[0].memo, 'base64'); let string = buffer.toString('hex');
    – Maxim Gaina
    Commented Jul 22, 2018 at 9:09
  • 1
    @JohanStén Of course you're right. Thank you for the correction.
    – Mister Ticot
    Commented Jul 23, 2018 at 3:00

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