Returns a wrapper around
ciphertextSource, such that any read-operation
via the wrapper results in AEAD-decryption of the underlying ciphertext,
using
associatedData as associated authenticated data.
The returned InputStream may support
mark()/
reset(),
but does not have to do it --
markSupported() provides the corresponding info.
The returned InputStream supports
skip(), yet possibly in an inefficient way,
i.e. by reading a sequence of blocks until the desired position. If a more efficient
skip()-functionality is needed, the Channel-based API can be used.