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I am using monero-nodejs liberary for rpc calls. I generated an integrated address and made a payment to this address.

By splitting the integrated address, I could see the paymentId is a33582a5a77c125b.

But when I check payments of this address, I get nothing (empty object)

Wallet.getPayments(req.params.id)

Do I need any decoding on this paymentId? I can see the tx mined.

  • 1
    Integrated payment IDs are encrypted. I don't know how to decrypt it however, but some advanced users might help. – el00ruobuob Aug 22 '18 at 6:49
  • I think I should change the title :) – Prashant Prabhakar Singh Aug 22 '18 at 6:52
  • @knaccc If you can help? – Prashant Prabhakar Singh Aug 22 '18 at 7:46
  • The payment id is stored in the tx_extra part of the transaction. To decode it you need to extract it, and then XOR it with (8a*R||0x8d) where a is your private view key, R is the transaction public key (which is also in tx_extra), || means concatenation, and * means elliptic curve scalar multiplication. I'm not familiar with this library, it looks like the maintainer will need to add this functionality. – knaccc Aug 22 '18 at 11:14
  • So everyone using this integrated address is using this complex maths to check if they received paymets correspoing to an integarted address? – Prashant Prabhakar Singh Aug 22 '18 at 12:42
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MyMonero provides a useful JavaScript library (mymonero-core-js) for dealing with this sort of thing.

Here is a code snippet that shows how to encrypt/decrypt a payment id using this bit of code from mymonero-core-js.

const mm = require('mymonero-core-js').monero_utils

const viewKey = mm.random_keypair()
const txKey = mm.random_keypair()
const paymentId = 'badc0ffeefabcafe'

const INTEGRATED_ID_SIZE = 8
const ENCRYPTED_PAYMENT_ID_TAIL = 0x8d

// If you have the private tx key and public view key
const pidKey = mm.cn_fast_hash(
  mm.generate_key_derivation(viewKey.pub, txKey.sec) +
  ENCRYPTED_PAYMENT_ID_TAIL.toString(16)
).slice(0, INTEGRATED_ID_SIZE * 2)

// If you have the private view key and public tx key
const pidKey2 = mm.cn_fast_hash(
  mm.generate_key_derivation(txKey.pub, viewKey.sec) +
  ENCRYPTED_PAYMENT_ID_TAIL.toString(16)
).slice(0, INTEGRATED_ID_SIZE * 2)

// Assert that the pidKeys are equal
console.log((pidKey === pidKey2)
  ? 'pidKeys are equal (expected)'
  : 'pidKeys are not equal (unexpected)')

// Encrypt Payment ID
const encryptedPaymentId = mm.hex_xor(paymentId, pidKey)
console.log('Encrypted: ' + encryptedPaymentId)

// Decrypt Payment ID
const decryptedPaymentId = mm.hex_xor(encryptedPaymentId, pidKey)
console.log('Decrypted: ' + decryptedPaymentId)

// Assert that the original and decrypted payment ids are equal
console.log((decryptedPaymentId === paymentId)
  ? 'Successful Decryption!'
  : 'Unsuccessful Decryption')

Should provide an output similar to:

pidKeys are equal (expected)
Encrypted: cfc3f2120b7db7c0
Decrypted: badc0ffeefabcafe
Successful Decryption!

Hope this helps!

  • Thanks. But I can see I get the same payment Id that I provided. I have encrypted payment Id , and I wish to decrypt it. Also, both encrypted and decrypted keys are of same length. But encrypted payment id is 16 chars where normal Payment ids is 106 chars. – Prashant Prabhakar Singh Aug 23 '18 at 6:38
  • No, payment IDs are either 32 bytes (64 hexadecimal characters) or 8 bytes (in the case of integrated addresses). As you asked about integrated addresses, the payment ID would be 8 bytes (or 16 chars as hex). There is no case where "Payment ids is 106 chars", whether encrypted, integrated, whatever. – jtgrassie Aug 23 '18 at 13:53

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