KMAC_128 / KMAC_128XOF

[NickBrighten]

The implementation of the KMAC is not compatible to KMAC_128 and KMAC_128XOF.

I don't know exactly where the error lies, but I suspect it is in the file kmac.c at line 164.

So you can try some online tools to evaluate - to eventually reproduce the error of the code:

https://hashonline.net/macs/kmac128/
https://emn178.github.io/online-tools/kmac128/
https://emn178.github.io/online-tools/kmacxof128/

https://www.lddgo.net/en/encrypt/kmac-calculate-verify (please enter the correct parameter)

The KMAC_256 and the KMAC_256_XOF works fine within the tools.

I can also not explain it in the NIST document here: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-185.pdf (at site 10)
Everything looks fine, but the results are very different.

Hope you can explain it and fix it.

[karel-m]

Could you post an example of the input data and parameters + the incorrect vs. expected outputs?

Our implementation could for sure contain a bug but our tests cover all the official NIST SP 800-185 KMAC128 samples.

[NickBrighten]

Of course:

so I have try it with the following parameters

Input: 0123456789abcdef (UTF-8)
Key: 0123456789abcdef (UTF-8)

No Customs.

Results from following sites:

https://www.lddgo.net/en/encrypt/kmac-calculate-verify

KMAC-128 - Output-Size: 256:
593010ec33ecd62dbf4550974bcd94ce1fcac86dcd2ccded148bf6d41e65909e

KMAC-128 - Output-Size: 128:
cd385658d52c75d8062804ae04f3937c

---

https://emn178.github.io/online-tools/kmac128/

KMAC-128 - Output-Size: 256:
593010ec33ecd62dbf4550974bcd94ce1fcac86dcd2ccded148bf6d41e65909e

KMAC-128 - Output-Size: 128:
cd385658d52c75d8062804ae04f3937c

KMAC-128-XOF - Output-Size 128:
25dcaf9dafcaaa484cc998fba96fa75e

KMAC-128-XOF - Output-Size 256:
25dcaf9dafcaaa484cc998fba96fa75ebbd4d6de1d59fd6e446185721e448254

---

https://hashonline.net/macs/kmac128/
cd385658d52c75d8062804ae04f3937c

---

and result from the code in libtomcrypt:

KMAC-128:
f663006cf738e8979380b7c23e63fc2e
or
6fe8215259cf3a9f980c0c2ec4d74cc0e8f7d1f8fe33c74d3701ca80aa8b4c90

and

KMAC-128-XOF:
5fb3ea23dee0a93c636e187d8bd9fb9f
or
5fb3ea23dee0a93c636e187d8bd9fb9fd2fc461befd28fb6b0133c657ed9f29a

[karel-m]

#include <tomcrypt.h>

int main(void)
{
   const unsigned char *key = (const unsigned char*)"0123456789abcdef";
   const unsigned char *in  = (const unsigned char*)"0123456789abcdef";
   unsigned char out[64];
   unsigned long outlen, j;

   outlen = 32;
   kmac_memory(LTC_KMAC128, key, 16, NULL, 0, in, 16, out, &outlen);
   printf("KMAC-128     output=256: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   outlen = 16;
   kmac_memory(LTC_KMAC128, key, 16, NULL, 0, in, 16, out, &outlen);
   printf("KMAC-128     output=128: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   outlen = 16;
   kmac_memory(LTC_KMAC128_XOF, key, 16, NULL, 0, in, 16, out, &outlen);
   printf("KMAC-128-XOF output=128: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   outlen = 32;
   kmac_memory(LTC_KMAC128_XOF, key, 16, NULL, 0, in, 16, out, &outlen);
   printf("KMAC-128-XOF output=256: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   return 0;
}

prints:

KMAC-128     output=256: 593010ec33ecd62dbf4550974bcd94ce1fcac86dcd2ccded148bf6d41e65909e
KMAC-128     output=128: cd385658d52c75d8062804ae04f3937c
KMAC-128-XOF output=128: 25dcaf9dafcaaa484cc998fba96fa75e
KMAC-128-XOF output=256: 25dcaf9dafcaaa484cc998fba96fa75ebbd4d6de1d59fd6e446185721e448254

[NickBrighten]

My programming is in Objective-C (64-Bit only):

#define _KMAC128 1
#define _KMAC256. 2
#define _KMAC128_XOF 3
#define _KMAC256_XOF 4

    unsigned long oL = _BIT_LENGTH_256;
    unsigned char out[oL];

    kmac_state s;
    kmac_init(_KMAC128, (const unsigned char *)[_key UTF8String], _key.length, 0, 0, &s);
    kmac_process(d.bytes, d.length, &s);
    kmac_done(out, &oL, &s);

    NSMutableString *pr;
    pr=[NSMutableString stringWithCapacity:oL*2];
    for(int i=0;i<oL;i++){[pr appendFormat:@"%02x",out[i]];}
    return pr;

[karel-m]

Same (correct) output with this code:

#include <tomcrypt.h>

int main(void)
{
   const unsigned char *key = (const unsigned char*)"0123456789abcdef";
   const unsigned char *in  = (const unsigned char*)"0123456789abcdef";
   unsigned char out[64];
   unsigned long outlen, j;
   kmac_state st;

   outlen = 32;
   kmac_init(&st, LTC_KMAC128, key, 16, NULL, 0);
   kmac_process(&st, in, 16);
   kmac_done(&st, out, &outlen);
   printf("KMAC-128     output=256: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   outlen = 16;
   kmac_init(&st, LTC_KMAC128, key, 16, NULL, 0);
   kmac_process(&st, in, 16);
   kmac_done(&st, out, &outlen);
   printf("KMAC-128     output=128: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   outlen = 16;
   kmac_init(&st, LTC_KMAC128_XOF, key, 16, NULL, 0);
   kmac_process(&st, in, 16);
   kmac_done(&st, out, &outlen);
   printf("KMAC-128-XOF output=128: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   outlen = 32;
   kmac_init(&st, LTC_KMAC128_XOF, key, 16, NULL, 0);
   kmac_process(&st, in, 16);
   kmac_done(&st, out, &outlen);
   printf("KMAC-128-XOF output=256: ");
   for (j = 0; j < outlen; ++j) printf("%02x", out[j]);
   printf("\n");

   return 0;
}

I am afraid I cannot help you with Objective-C.