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@@ -0,0 +1,61 @@
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+from poseidon import poseidon_hash
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+
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+
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+def xor(text, key):
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+ ciphertext = ""
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+ for i in range(len(text)):
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+ ciphertext += chr(ord(text[i]) ^^ ord(key[i % len(key)]))
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+
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+ return ciphertext
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+
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+
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+p = 0x40000000000000000000000000000000224698fc094cf91b992d30ed00000001
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+q = 0x40000000000000000000000000000000224698fc0994a8dd8c46eb2100000001
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+Fp = GF(p)
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+Fq = GF(q)
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+Ep = EllipticCurve(Fp, (0, 5))
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+Ep.set_order(q)
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+
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+nfk_x = 0x25e7aa169ca8198d2e375571faf4c9cf5e7eb192ccb5db9bd36f6aa7e447ca75
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+nfk_y = 0x155c1f851b1a3384880473442008ff755fe0a49ec1c1b4332db8dce21ae001cc
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+G = Ep([nfk_x, nfk_y])
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+
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+# Alice's view key pair
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+a = Fq.random_element()
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+A = a * G
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+
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+# Alice's spend key pair
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+b = Fq.random_element()
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+B = b * G
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+
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+# Each output in a transaction has its own public key
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+# r is a "transaction secret key, unique to the transaction
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+# and known only to the sender.
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+r = Fq.random_element()
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+R = r * G
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+
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+# The public key for the output is calculated as such:
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+rA = r * A
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+rA_x, rA_y = rA.xy()
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+P = Fq(int(poseidon_hash([rA_x, rA_y]))) * G + B
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+
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+# Output value
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+value = "10000"
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+# Sender encrypts it
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+value_enc = xor(value, str(rA))
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+
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+# A recipient scanning for txs will look at R and calculate
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+# for themselves what an output would look like if it was
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+# destined for them:
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+aR = a * R
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+aR_x, aR_y = aR.xy()
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+P_ = Fq(int(poseidon_hash([aR_x, aR_y]))) * G + B
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+assert P == P_
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+
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+# Recipient decrypts ciphertext
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+value_ = xor(value_enc, str(aR))
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+assert value == value_
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+
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+# The secret key for spending the output is: H(aR) + b
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+# And outputs can only be spent by providing a signature
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+# for the output.
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parazyd