Cipher Mode SIV

[NickBrighten]

I understand the API to integrate SIV mode, but I don't understand what the purpose of the adnum (siv_encrypt_memory) parameter is. What does this parameter refer to within the API? Are there several different providers that work with different values ​​and/or is this an individual parameter that is set by the USER? I can't find any real information about this in the RFC docs (https://datatracker.ietf.org/doc/html/rfc5297).

Can you tell me what this parameter stands for in your API?

[sjaeckel]

It's explained in https://github.com/libtom/libtomcrypt/blob/develop/doc/crypt.tex#L2573 ff. You can download the latest version of the docs from CI or build it yourself with make docs.

In case something is unclear please feel free to point it out.

[NickBrighten]

Which element is meant?

The number of AAD elements is passed in \textit{adnum}

I'm passing the AAD and its length—what is the size of adnum now? I don't understand which element this is supposed to be.

[NickBrighten]

In case something is unclear please feel free to point it out.

Let us point it out:

Cipher: AES-128
Key: 0123456789abcdef (Key have to double, also from 128-bits to 256-bits - I have to pad with zero to 256-bits)
AAD: 0123456789abcdef (i don´t know if SIV needs 126-bits or unlimited - pass 128-bits)
PT: 0123456789abcdef

adnum : AAD.length (in this case 16 Bytes)

OUT: o2Ed0dKt2ME9E6eINUO8vBAs4xV0ENt8IIhr3w4Wxbo= (base64 encode)

Cipher: AES-128
Key: 0123456789abcdef (Key have to double, also from 128-bits to 256-bits - I have to pad with zero to 256-bits)
AAD: 0123456789abcdef (i don´t know if SIV needs 126-bits or unlimited - pass 128-bits)
PT: 0123456789abcdef

adnum : AAD.length/8 (in this case 2 Bytes)

OUT: zL9ULQBQjuohmxKweAlvdVe2M46phcjcSC6YQqV5CNk= (base64 encode)

Cipher: AES-128
Key: 0123456789abcdef0123456789abcdef (256-bits)
AAD: 0123456789abcdef (i don´t know if SIV needs 126-bits or unlimited - pass 128-bits)
PT: 0123456789abcdef

adnum : AAD.length (in this case 16 Bytes)

OUT: o2Ed0dKt2ME9E6eINUO8vNj60HMjy5da2OpZi4nESoo= (base64 encode)

Cipher: AES-128
Key: 0123456789abcdef0123456789abcdef (256-bits)
AAD: 0123456789abcdef (i don´t know if SIV needs 126-bits or unlimited - pass 128-bits)
PT: 0123456789abcdef

adnum : AAD.length/8 (in this case 2 Bytes)

OUT: zL9ULQBQjuohmxKweAlvdfb5YITuInzwg5XLHc6tdUQ= (base64 encode)

I don't know if the results are correct.