# Key-image generation: What does p signify in I = xHp(P)?

According to the CN whitepaper key image I is generated thusly:

I = xHp(P)

I understand P is the one-time public key for the transaction, x the corresponding private key and H a deterministic hash function, but what is p?

Thanks

• FYI, you can use H<sub>p</sub> (although not in a code section). – assylias Apr 11 '17 at 14:24