Questions about Ciphers

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Questions about Ciphers

Patrice Guérin-2
Hello,

I have two questions :
  • I use OBJ_NAME_do_all_sorted() with  OBJ_NAME_TYPE_CIPHER_METH to get the list of supported cipher methods
    Is there a difference between lowercase and uppercase names ?
    I've noticed that some do not have uppercase name (ex. aes-128-ccm)
    Is there a prefered name to use ?
  • In the case of GCM usage (with examples found in the OpenSSL wiki),
    Is the specific control action to set the tag on decryption can be done at the beginning rather than juste before EVP_DecryptFinal_ex() ?
Thank you.
Kind regards,
Patrice.


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Re: Questions about Ciphers

Matt Caswell-2


On 14/02/2019 16:42, Patrice Guérin wrote:
> Hello,
>
> I have two questions :
>
>   * I use OBJ_NAME_do_all_sorted() with  OBJ_NAME_TYPE_CIPHER_METH to get the
>     list of supported cipher methods
>     Is there a difference between lowercase and uppercase names ?
>     I've noticed that some do not have uppercase name (ex. aes-128-ccm)
>     Is there a prefered name to use ?

Objects have a "short name" and a "long name". In many cases the two are
identical. In others they have minor differences such as uppercase vs lowercase.
It doesn't matter - both forms refer to the same object. You can use either.

>   * In the case of GCM usage (with examples found in the OpenSSL wiki),
>     Is the specific control action to set the tag on decryption can be done at
>     the beginning rather than juste before EVP_DecryptFinal_ex() ?

Yes, as long as it's done after EVP_DecryptInit_ex().

Matt

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