@node en34132015
@section Cipher modes of operation

@ref{en2814789, GOST 28147-89} standard defines the following modes of
operation for Magma cipher:
@itemize
    @item ECB
    @item CFB
    @item CTR
    @item MAC
@end itemize

@strong{Features}:
@itemize
@item 28147-89 MAC is completely unusable:
    @itemize
        @item Reduced 16-round Magma cipher is used instead of 32 one.
        @item Authenticating data does not have neither padding, nor
        length specifying, so @code{MAC(0xDEAD) = MAC(0xDEAD00)}.
    @end itemize
@item Specified counter (CTR) mode increments counters with predefined
constants for 32-bit halves of the block. This differs from simpler
counter mode implementations.
@end itemize

Modern @strong{GOST R 34.13-2015} standard defines the following modes
of operation:
@itemize
@item ECB
@item CBC
@item OFB
@item CFB
@item CTR
@item MAC
@end itemize

@strong{Features}:
@itemize
@item Common simple counter mode implementation.
@item Specified MAC is identical to
@url{https://en.wikipedia.org/wiki/CMAC, CMAC} and can be used safely.
@end itemize