50 52 4f 47 52 41 4d 4d 45

On OS X, trust can be revoked from either of the CNNIC root certificates or from any certificate in the Allow List using the following steps:

• Find the certificate you wish to never trust. For example, click on the lock icon in Safari and then drag the icon of the certificate to a location on your desktop.
• Double-click on the certificate to open it in Keychain Access. For leaf certificates, you will need to double-click the certificate to open it. In the case of root certificates, you will be prompted upon import into Keychain Access.
• Change the trust setting to Never Trust.

You can find the version of the Trust Store installed on your iOS device by tapping Settings > General > About. Scroll down to the bottom of the list to see the Trust Store version. 

For a complete list of trusted certificates, see the OS X Trust Store and iOS Trust Store.

Thank you for the replay,

I have checked my code by passing the some values and verified with the CRC calculator in online. i checked by as you suggested to put the seed to the next CRC calculation, value Below are the test scenarios,

a) passed ‘1’ (0x31) got the correct value as CRC calculator,

b) Passed ‘2’ , and passed the CRC of ‘1’  as seed, i got 0x3DBA from code. i verifed the same by passing ’12’ at a same time in the CRC calculator.

But i am not getting to calculate the CRC to my downloaded file, from where i need to pass the data. file starts as,

@58005C 52 @5805FF 01 00 1A 5F FE 5C 0B 5D 01 00 00 00 19 50 0500 01 00 1A 5F 0C 5D 0B 5D 00 00 00 00 19 50 0600 01 00 1A 5F 17 5D 0B 5D 00 00 00 00 19 50 0700 02 00 1A 5F 25 5D 0B 5D 16 00 00 00 18 50 0100 01 00 3C 5F 2E 5D 0B 5D 01 00 00 00 BC 4D 0100 03 00 42 5F 0B 5D 0B 5D 02 00 00 00 7E 4D 0400 00 00 21 5F 40 5D 0B 5D 00 00 00 00 1F 4E 0800 00 00 21 5F 4B 5D 56 5D 00 00 00 00 0F 4E 1000 00 00 21 5F 63 5D 6D 5D 00 00 00 00 EB 4D 24

here 5C52 is CRC of the file, from where do i need to pass the data whether from @5800 or from @5805 or FF 01 00. i am got confused here. Please suggest.