What does PIN encrypted under LMK mean? From what I understand the Local Master Key is only there to encrypt other keys. I was reading some code and I saw function names like encryptClearToLmk or decryptLmkToClear.
Does the expression have something to do with the LMK key pairs?
In short, no, because the LMK is a single key. The Hardware Security Module (HSM) has it's own master key called the LMK, and this is generally not dealt with in the clear. Any keys you generate will be done so using that LMK. The functions you mentioned are used to encrypt and decrypt to/from ciphertext from/to plaintext, both procedures of which use the LMK as a shared secret to either function. The LMK is also a symmetric key, not asymmetric. This is a gross oversimplification, but if you would like to learn more about this, take a look at the following link:
https://github.com/jpos/jPOS/wiki/HSM_basics (original page archive)
Hope this sets you on the right track.
