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md6, a (forgotten?) SHA-3 contender

This implements md6 for OpenSSL 3, following the md6 report and using an the original optimized implementation.

This implementation doesn't support keyed hashes (yet).

Algorithm Names

The following names can be used with EVP_MD_fetch(3)

  • md6

    This is the main unqualified algorithm name.

  • md6-128

  • md6-224

  • md6-256

  • md6-384

  • md6-512

    These are variants of md6, qualified with the hash output size expressed in bits.

Properties

The following properties can be used to distinguish this particular implementation of md6 when fetching it with EVP_MD_fetch(3):

  • x.author=@levitte
  • provider=extra

Algorithm parameters

These parameters can be retrieved using EVP_MD_gettable_params(3) and EVP_MD_get_params(3):

  • "size" <unsigned integer>

    The standard hash output size, expressed in number of bytes.

    For the "md6" algorithm name, this size is unset (zero) unless the environment variable MD6_BITS is set, see the description of Environment below.

    For the "md6" algorithm variants that include a hash output size in bits, the number received with this parameter is calculated from that number of bits.

    The function EVP_MD_get_size(3) uses this parameter implicitly.

  • "rounds" <unsigned integer>

    The standard number of rounds, calculated from the standard hash output size.

    This is called r in the md6 report.

  • "mode" <unsigned integer>

    The md6 operation mode.

    This is called L in the md6 report.

Algorithm context parameters

These parameters can be retrieved using EVP_MD_CTX_gettable_params(3), EVP_MD_CTX_get_params(3), EVP_MD_CTX_settable_params(3), and EVP_MD_CTX_set_params(3).

  • "size" <unsigned integer>

    The hash output size, expressed in number of bytes.

    For the "md6" algorithm variants that include a hash output size in bits, the number received with this parameter is calculated from that number of bits and cannot be changed.

    The function EVP_MD_CTX_get_size(3) uses this parameter implicitly.

  • "rounds" <unsigned integer>

    The number of rounds.

    This is called r in the md6 report.

  • "mode" <unsigned integer>

    The md6 operation mode.

    This is called L in the md6 report.

Environment

Defaults can be set for these parameters using environment variables:

  • MD6_BITS

    The hash output size in bits.

    This is called d in the md6 report.

  • MD6_ROUNDS

    The number of rounds.

    This is called r in the md6 report.

  • MD6_MODE

    The mode parameter.

    This is called L in the md6 report.

Example command line usage

These examples all assume that extra.so / extra.dll is located in the current directory.

  • Using the md6 variants with explicit hash output size and modified number of rounds:

    $ echo -n 'abc' \
  | MD6_ROUNDS=5 openssl dgst \
      -provider-path . -provider extra -md6-256
md6-256(stdin)= 8854c14dc284f840ed71ad7ba542855ce189633e48c797a55121a746be48cec8

  • Same as above, but setting the hash output size with MD6_BITS:

    $ echo -n 'abc' \
  | MD6_BITS=256 MD6_ROUNDS=5 openssl dgst \
      -provider-path . -provider extra -md6
md6(stdin)= 8854c14dc284f840ed71ad7ba542855ce189633e48c797a55121a746be48cec8