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The Bouncy Castle Java APIs for the OpenPGP Protocol. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.

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package org.bouncycastle.bcpg;

public class CRC24
{
    protected static final int CRC24_INIT = 0x0b704ce;
    protected static final int CRC24_POLY = 0x1864cfb;

    protected int crc = CRC24_INIT;

    /**
     * Default, iterative CRC-24 implementation as described in RFC4880.
     * This implementation mimics the use of a feedback shift register in software.
     *
     * @see 
     * RFC4880 §6.1. An Implementation of the CRC-24 in "C"
     */
    public CRC24()
    {
    }

    public void update(
        int b)
    {
        crc ^= b << 16;
        for (int i = 0; i < 8; i++)
        {
            crc <<= 1;
            if ((crc & 0x1000000) != 0)
            {
                crc ^= CRC24_POLY;
            }
        }
    }

    public int getValue()
    {
        return crc & 0xFFFFFF;
    }

    public void reset()
    {
        crc = CRC24_INIT;
    }
}