[FFmpeg-devel] libavutil: added camellia block cipher

[Michael Niedermayer]

On Fri, Dec 26, 2014 at 08:48:27PM +0530, supraja reddy wrote:
> Hello,
> 
> I made a small change in the decrypt function which I should have done so
> earlier.
> Please let me know of the further changes/fixes.
> 
> Thanks,
> 
> Supraja
> 

[...]

> +static uint64_t F(uint64_t F_IN, uint64_t KE)
> +{
> +    uint32_t Zl, Zr;

> +    Zl = (F_IN >> 32) ^ (KE >> 32);
> +    Zr = (F_IN & MASK32) ^ (KE & MASK32);

KE ^= F_IN;
Zl = KE >> 32;
Zr = KE & MASK32;


> +    Zl = ((SBOX1[(Zl >> 24) & MASK8] << 24) | (SBOX2[(Zl >> 16) & MASK8] << 16) |(SBOX3[(Zl >> 8) & MASK8] << 8) |(SBOX4[Zl & MASK8]));
> +    Zr = ((SBOX2[(Zr >> 24) & MASK8] << 24) | (SBOX3[(Zr >> 16) & MASK8] << 16) |(SBOX4[(Zr >> 8) & MASK8] << 8) |(SBOX1[Zr & MASK8]));

(Zl >> 24) and (Zr >> 24) are limited to 8bit they should not need
& MASK8

((uint32_t)SBOX1[Zl >> 24]) << 24)

it would also be possible to reduce the number of operations at the
expense of larger tables but iam not sure that would be a good idea


[...]

> +static const int shift1[2][6] = {
> +    {0, 15, 30, 17, 17, 17},
> +    {0, 15, 15, 15, 34, 17}
> +};
> +static const int pos1[2][6] = {
> +    {0, 4, 10, 16, 18, 22},
> +    {2, 6, 8, 14, 20, 24}
> +};
> +static const int pos2[4][4]= {
> +    {0, 12, 16, 22},
> +    {6, 14, 24, 28},
> +    {2, 10, 20, 32},
> +    {4, 8, 18, 26}
> +};
> +static const int shift2[4][5]= {
> +    {0, 45, 15, 17},
> +    {15, 30, 32, 17},
> +    {0, 30, 30, 51},
> +    {15, 15, 30, 34}
> +};

these could be made uint8_t

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored answer#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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