In block cipher modes of operation for encryption on input of a plaintext of $N$ blocks (We assume that the input size is always a multiple of the blockcipher mode: $N·16$ bytes) the size of the ciphertext is $N+1$, where the extra block is the IV.
Is there an efficient way to have fixed (parametrizable) larger length output on variable length input, to hide the plaintext size?
For example, for a short plaintext of $16$ or $20$ bytes I want to generate a larger ciphertext like 128 bytes, so an attacker can't learn the plaintext size from the ciphertext size.
The only way I can think of is just to produce pseudo-random pad to increase the plaintext message to equal the size of the ciphertext you want to output.