Crypto algorithm block size in octets.
If plaintext and ciphertext have different lengths, the longer length is considered.
counterBits
counterBits:number
Number of counter bits.
Optionalfixed
fixed?:bigint|Uint8Array
Fixed portion.
Remarks
Required if fixedBits is positive.
This may be specified as a bigint or a Uint8Array.
If it's a Uint8Array, it must have at least fixedBits bits.
The least significant bits are taken.
Options for Initialization Vectors using fixed+random+counter structure.
IVs following this construction method have three parts: