Manual Pages for UNIX Operating System command usage for man EVP_md2

OpenSSL                                  EVP_DigestInit(3openssl)



NNNNAAAAMMMMEEEE
     EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex,
     EVP_DigestUpdate, EVP_DigestFinal_ex, EVP_MD_CTX_cleanup,
     EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE, EVP_MD_CTX_copy_ex,
     EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size,
     EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size,
     EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_md_null,
     EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_dss, EVP_dss1,
     EVP_mdc2, EVP_ripemd160, EVP_get_digestbyname,
     EVP_get_digestbynid, EVP_get_digestbyobj - EVP digest
     routines

SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
      #include 

      void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
      EVP_MD_CTX *EVP_MD_CTX_create(void);

      int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
      int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
      int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
             unsigned int *s);

      int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
      void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);

      int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);

      int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
      int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
             unsigned int *s);

      int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);

      #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */

      #define EVP_MD_type(e)                 ((e)->type)
      #define EVP_MD_pkey_type(e)            ((e)->pkey_type)
      #define EVP_MD_size(e)                 ((e)->md_size)
      #define EVP_MD_block_size(e)           ((e)->block_size)

      #define EVP_MD_CTX_md(e)               (e)->digest)
      #define EVP_MD_CTX_size(e)             EVP_MD_size((e)->digest)
      #define EVP_MD_CTX_block_size(e)       EVP_MD_block_size((e)->digest)
      #define EVP_MD_CTX_type(e)             EVP_MD_type((e)->digest)










16/Oct/2009            Last change: 0.9.8o                      1






OpenSSL                                  EVP_DigestInit(3openssl)



      const EVP_MD *EVP_md_null(void);
      const EVP_MD *EVP_md2(void);
      const EVP_MD *EVP_md5(void);
      const EVP_MD *EVP_sha(void);
      const EVP_MD *EVP_sha1(void);
      const EVP_MD *EVP_dss(void);
      const EVP_MD *EVP_dss1(void);
      const EVP_MD *EVP_mdc2(void);
      const EVP_MD *EVP_ripemd160(void);

      const EVP_MD *EVP_get_digestbyname(const char *name);
      #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
      #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))


DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     The EVP digest routines are a high level interface to
     message digests.

     EVP_MD_CTX_init() initializes digest context ccccttttxxxx.

     EVP_MD_CTX_create() allocates, initializes and returns a
     digest context.

     EVP_DigestInit_ex() sets up digest context ccccttttxxxx to use a
     digest ttttyyyyppppeeee from ENGINE iiiimmmmppppllll. ccccttttxxxx must be initialized before
     calling this function. ttttyyyyppppeeee will typically be supplied by a
     functionsuch as EVP_sha1().  If iiiimmmmppppllll is NULL then the
     default implementation of digest ttttyyyyppppeeee is used.

     EVP_DigestUpdate() hashes ccccnnnntttt bytes of data at dddd into the
     digest context ccccttttxxxx. This function can be called several
     times on the same ccccttttxxxx to hash additional data.

     EVP_DigestFinal_ex() retrieves the digest value from ccccttttxxxx and
     places it in mmmmdddd. If the ssss parameter is not NULL then the
     number of bytes of data written (i.e. the length of the
     digest) will be written to the integer at ssss, at most
     EEEEVVVVPPPP_MMMMAAAAXXXX_MMMMDDDD_SSSSIIIIZZZZEEEE bytes will be written.  After calling
     EVP_DigestFinal_ex() no additional calls to
     EVP_DigestUpdate() can be made, but EVP_DigestInit_ex() can
     be called to initialize a new digest operation.

     EVP_MD_CTX_cleanup() cleans up digest context ccccttttxxxx, it should
     be called after a digest context is no longer needed.

     EVP_MD_CTX_destroy() cleans up digest context ccccttttxxxx and frees
     up the space allocated to it, it should be called only on a
     context created using EVP_MD_CTX_create().

     EVP_MD_CTX_copy_ex() can be used to copy the message digest
     state from iiiinnnn to oooouuuutttt. This is useful if large amounts of



16/Oct/2009            Last change: 0.9.8o                      2






OpenSSL                                  EVP_DigestInit(3openssl)



     data are to be hashed which only differ in the last few
     bytes. oooouuuutttt must be initialized before calling this function.

     EVP_DigestInit() behaves in the same way as
     EVP_DigestInit_ex() except the passed context ccccttttxxxx does not
     have to be initialized, and it always uses the default
     digest implementation.

     EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except
     the digest context ccccttttxxxx is automatically cleaned up.

     EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except
     the destination oooouuuutttt does not have to be initialized.

     EVP_MD_size() and EVP_MD_CTX_size() return the size of the
     message digest when passed an EEEEVVVVPPPP_MMMMDDDD or an EEEEVVVVPPPP_MMMMDDDD_CCCCTTTTXXXX
     structure, i.e. the size of the hash.

     EVP_MD_block_size() and EVP_MD_CTX_block_size() return the
     block size of the message digest when passed an EEEEVVVVPPPP_MMMMDDDD or an
     EEEEVVVVPPPP_MMMMDDDD_CCCCTTTTXXXX structure.

     EVP_MD_type() and EVP_MD_CTX_type() return the NID of the
     OBJECT IDENTIFIER representing the given message digest when
     passed an EEEEVVVVPPPP_MMMMDDDD structure.  For example
     EVP_MD_type(EVP_sha1()) returns NNNNIIIIDDDD_sssshhhhaaaa1111. This function is
     normally used when setting ASN1 OIDs.

     EVP_MD_CTX_md() returns the EEEEVVVVPPPP_MMMMDDDD structure corresponding
     to the passed EEEEVVVVPPPP_MMMMDDDD_CCCCTTTTXXXX.

     EVP_MD_pkey_type() returns the NID of the public key signing
     algorithm associated with this digest. For example
     EVP_sha1() is associated with RSA so this will return
     NNNNIIIIDDDD_sssshhhhaaaa1111WWWWiiiitttthhhhRRRRSSSSAAAAEEEEnnnnccccrrrryyyyppppttttiiiioooonnnn. This "link" between digests and
     signature algorithms may not be retained in future versions
     of OpenSSL.

     EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and
     EVP_ripemd160() return EEEEVVVVPPPP_MMMMDDDD structures for the MD2, MD5,
     SHA, SHA1, MDC2 and RIPEMD160 digest algorithms
     respectively. The associated signature algorithm is RSA in
     each case.

     EVP_dss() and EVP_dss1() return EEEEVVVVPPPP_MMMMDDDD structures for SHA
     and SHA1 digest algorithms but using DSS (DSA) for the
     signature algorithm.

     EVP_md_null() is a "null" message digest that does nothing:
     i.e. the hash it returns is of zero length.





16/Oct/2009            Last change: 0.9.8o                      3






OpenSSL                                  EVP_DigestInit(3openssl)



     EVP_get_digestbyname(), EVP_get_digestbynid() and
     EVP_get_digestbyobj() return an EEEEVVVVPPPP_MMMMDDDD structure when passed
     a digest name, a digest NID or an ASN1_OBJECT structure
     respectively. The digest table must be initialized using,
     for example, OpenSSL_add_all_digests() for these functions
     to work.

RRRREEEETTTTUUUURRRRNNNN VVVVAAAALLLLUUUUEEEESSSS
     EVP_DigestInit_ex(), EVP_DigestUpdate() and
     EVP_DigestFinal_ex() return 1 for success and 0 for failure.

     EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for
     failure.

     EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return
     the NID of the corresponding OBJECT IDENTIFIER or NID_undef
     if none exists.

     EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e),
     EVP_MD_size(), EVP_MD_CTX_block_size()  and
     EVP_MD_block_size() return the digest or block size in
     bytes.

     EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(),
     EVP_dss(), EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return
     pointers to the corresponding EVP_MD structures.

     EVP_get_digestbyname(), EVP_get_digestbynid() and
     EVP_get_digestbyobj() return either an EEEEVVVVPPPP_MMMMDDDD structure or
     NULL if an error occurs.

NNNNOOOOTTTTEEEESSSS
     The EEEEVVVVPPPP interface to message digests should almost always be
     used in preference to the low level interfaces. This is
     because the code then becomes transparent to the digest used
     and much more flexible.

     SHA1 is the digest of choice for new applications. The other
     digest algorithms are still in common use.

     For most applications the iiiimmmmppppllll parameter to
     EVP_DigestInit_ex() will be set to NULL to use the default
     digest implementation.

     The functions EVP_DigestInit(), EVP_DigestFinal() and
     EVP_MD_CTX_copy() are obsolete but are retained to maintain
     compatibility with existing code. New applications should
     use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
     EVP_MD_CTX_copy_ex() because they can efficiently reuse a
     digest context instead of initializing and cleaning it up on
     each call and allow non default implementations of digests
     to be specified.



16/Oct/2009            Last change: 0.9.8o                      4






OpenSSL                                  EVP_DigestInit(3openssl)



     In OpenSSL 0.9.7 and later if digest contexts are not
     cleaned up after use memory leaks will occur.

EEEEXXXXAAAAMMMMPPPPLLLLEEEE
     This example digests the data "Test Message\n" and "Hello
     World\n", using the digest name passed on the command line.

      #include 
      #include 

      main(int argc, char *argv[])
      {
      EVP_MD_CTX mdctx;
      const EVP_MD *md;
      char mess1[] = "Test Message\n";
      char mess2[] = "Hello World\n";
      unsigned char md_value[EVP_MAX_MD_SIZE];
      int md_len, i;

      OpenSSL_add_all_digests();

      if(!argv[1]) {
             printf("Usage: mdtest digestname\n");
             exit(1);
      }

      md = EVP_get_digestbyname(argv[1]);

      if(!md) {
             printf("Unknown message digest %s\n", argv[1]);
             exit(1);
      }

      EVP_MD_CTX_init(&mdctx);
      EVP_DigestInit_ex(&mdctx, md, NULL);
      EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
      EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
      EVP_DigestFinal_ex(&mdctx, md_value, &md_len);
      EVP_MD_CTX_cleanup(&mdctx);

      printf("Digest is: ");
      for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
      printf("\n");
      }


BBBBUUUUGGGGSSSS
     The link between digests and signing algorithms results in a
     situation where EVP_sha1() must be used with RSA and
     EVP_dss1() must be used with DSS even though they are
     identical digests.




16/Oct/2009            Last change: 0.9.8o                      5






OpenSSL                                  EVP_DigestInit(3openssl)



SSSSEEEEEEEE AAAALLLLSSSSOOOO
     evp(3), hmac(3), md2(3), md5(3), mdc2(3), ripemd(3), sha(3),
     dgst(1)

HHHHIIIISSSSTTTTOOOORRRRYYYY
     EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal()
     are available in all versions of SSLeay and OpenSSL.

     EVP_MD_CTX_init(), EVP_MD_CTX_create(),
     EVP_MD_CTX_copy_ex(), EVP_MD_CTX_cleanup(),
     EVP_MD_CTX_destroy(), EVP_DigestInit_ex() and
     EVP_DigestFinal_ex() were added in OpenSSL 0.9.7.

     EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(),
     EVP_dss(), EVP_dss1(), EVP_mdc2() and EVP_ripemd160() were
     changed to return truely const EVP_MD * in OpenSSL 0.9.7.







































16/Oct/2009            Last change: 0.9.8o                      6