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- from poseidon import poseidon_hash
- def xor(text, key):
- ciphertext = ""
- for i in range(len(text)):
- ciphertext += chr(ord(text[i]) ^^ ord(key[i % len(key)]))
- return ciphertext
- p = 0x40000000000000000000000000000000224698fc094cf91b992d30ed00000001
- q = 0x40000000000000000000000000000000224698fc0994a8dd8c46eb2100000001
- Fp = GF(p)
- Fq = GF(q)
- Ep = EllipticCurve(Fp, (0, 5))
- Ep.set_order(q)
- nfk_x = 0x25e7aa169ca8198d2e375571faf4c9cf5e7eb192ccb5db9bd36f6aa7e447ca75
- nfk_y = 0x155c1f851b1a3384880473442008ff755fe0a49ec1c1b4332db8dce21ae001cc
- G = Ep([nfk_x, nfk_y])
- # Alice's view key pair
- a = Fq.random_element()
- A = a * G
- # Alice's spend key pair
- b = Fq.random_element()
- B = b * G
- # Each output in a transaction has its own public key
- # r is a "transaction secret key, unique to the transaction
- # and known only to the sender.
- r = Fq.random_element()
- R = r * G
- # The public key for the output is calculated as such:
- rA = r * A
- rA_x, rA_y = rA.xy()
- P = Fq(int(poseidon_hash([rA_x, rA_y]))) * G + B
- # Output value
- value = "10000"
- # Sender encrypts it
- value_enc = xor(value, str(rA))
- # A recipient scanning for txs will look at R and calculate
- # for themselves what an output would look like if it was
- # destined for them:
- aR = a * R
- aR_x, aR_y = aR.xy()
- P_ = Fq(int(poseidon_hash([aR_x, aR_y]))) * G + B
- assert P == P_
- # Recipient decrypts ciphertext
- value_ = xor(value_enc, str(aR))
- assert value == value_
- # The secret key for spending the output is: H(aR) + b
- # And outputs can only be spent by providing a signature
- # for the output.
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