Checked this link: https://moneroblocks.info/api/get_transaction_data/4adb55cde1ffcc0ea639b6718355c48c0e574000306d95ef857e55d91ddabcf2

I could not find the encrypted mask value.

I believe the encrypted amount is in the ecdh part:

     "ecdhInfo": [
          "amount": "f350bbedb3a4a93b"
          "amount": "c2005984b560da47"
          "amount": "6a2a649c8322d6e1"
          "amount": "0e0c6e72d16779c7"

As of the March 2019 hard fork, commitment masks are deterministically derived from the per-output shared secret. This means the ECDHinfo part of the transaction will no longer store the encrypted mask.

See the commit here: https://github.com/monero-project/monero/commit/7d375981584e5ddac4ea6ad8879e2211d465b79d

Therefore, to determine the commitment mask, calculate:

commitment mask = Hs("commitment_mask" || Hs(8aR||i))

To reduce the storage requirement for the amount from 32 bytes to 8 bytes, the 8 byte amount is now XOR encrypted using an 8 byte key deterministically derived from the shared secret.

To encrypt the amount, calculate:

encrypted amount = 8 byte amount XOR first 8 bytes of keccak("amount" || Hs(8rA||i))

To decrypt the amount, calculate:

amount = 8 byte encrypted amount XOR first 8 bytes of keccak("amount" || Hs(8aR||i))

  • TBC: a is the public view key, i is the index of the output in the transaction – WeCanBeFriends May 26 '19 at 21:11
  • a is the private view key, not public. – jtgrassie May 26 '19 at 22:10
  • Oh right, 8aR is the public view key – WeCanBeFriends May 26 '19 at 22:24
  • 8aR is not "the public view key" either. R is the tx public key (the shared part of the shared secret), a is the receivers private view key and i is the output index. – jtgrassie May 27 '19 at 0:24
  • 1
    @WeCanBeFriends You're right, I've fixed the error in my answer. The shared secret is Hs(8aR||i) and not Hs(8aR||i)G. From a cryptographic point of view, it would also have worked to have chosen to directly use (8aR||i) instead of Hs(8aR||i) (inside these hashed constructions only), but since the code already calculates Hs(8aR||i) for use elsewhere, we just re-use it for simplicity. – knaccc May 27 '19 at 4:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.