Wraps an encrypted OpenFHE ciphertext. Supports arithmetic operators
+, -, * which dispatch to homomorphic operations.
Value
An S7 object of class Ciphertext, inheriting from OpenFHEObject,
whose ptr property holds an external pointer to the C++
ciphertext. Ciphertexts are produced by encrypt() and by the
eval_*() family rather than by calling this constructor directly,
and they carry the encrypted vector together with the level and
scaling-factor bookkeeping the scheme needs.