This Advanced Encryption Standard (AES) algorithm parameter ASN.1 type AES-IV is defined as

    AES-IV ::= OCTET STRING (SIZE(16))

A value of type AES-IV is encoded using the XML Encoding Rules (XER) of ASN.1 as

    <AES-IV>00000000000000000000000000000000</AES-IV>

A value of type AES-IV can also be encoded in a compact binary format using the Distinguished Encoding Rules (DER) of ASN.1. This Tag-Length-Value (TLV) hexadecimal representation of the same abstract value is encoded as

    041000000000000000000000000000000000

Also see CFBParameters and NumberOfBits.