EVP_DigestInit(3)            OpenSSL            EVP_DigestInit(3)


     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_DigestInit, EVP_DigestFinal, 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_sha224, EVP_sha256,
     EVP_sha384, EVP_sha512, EVP_dss, EVP_dss1, EVP_mdc2,
     EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid,
     EVP_get_digestbyobj - EVP digest routines


      #include <openssl/evp.h>

      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 64     /* SHA512 */

      int EVP_MD_type(const EVP_MD *md);
      int EVP_MD_pkey_type(const EVP_MD *md);
      int EVP_MD_size(const EVP_MD *md);
      int EVP_MD_block_size(const EVP_MD *md);

      const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
      #define EVP_MD_CTX_size(e)             EVP_MD_size(EVP_MD_CTX_md(e))
      #define EVP_MD_CTX_block_size(e)       EVP_MD_block_size((e)->digest)
      #define EVP_MD_CTX_type(e)             EVP_MD_type((e)->digest)

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EVP_DigestInit(3)            OpenSSL            EVP_DigestInit(3)

      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_sha224(void);
      const EVP_MD *EVP_sha256(void);
      const EVP_MD *EVP_sha384(void);
      const EVP_MD *EVP_sha512(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))


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

     EVP_MD_CTX_init() initializes digest context ctx.

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

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

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

     EVP_DigestFinal_ex() retrieves the digest value from ctx and
     places it in md. If the s 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 s, at most
     EVP_MAX_MD_SIZE 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 ctx, it should
     be called after a digest context is no longer needed.

     EVP_MD_CTX_destroy() cleans up digest context ctx and frees
     up the space allocated to it, it should be called only on a

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EVP_DigestInit(3)            OpenSSL            EVP_DigestInit(3)

     context created using EVP_MD_CTX_create().

     EVP_MD_CTX_copy_ex() can be used to copy the message digest
     state from in to out. This is useful if large amounts of
     data are to be hashed which only differ in the last few
     bytes. out must be initialized before calling this function.

     EVP_DigestInit() behaves in the same way as
     EVP_DigestInit_ex() except the passed context ctx 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 ctx is automatically cleaned up.

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

     EVP_MD_size() and EVP_MD_CTX_size() return the size of the
     message digest when passed an EVP_MD or an EVP_MD_CTX
     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 EVP_MD or an
     EVP_MD_CTX structure.

     EVP_MD_type() and EVP_MD_CTX_type() return the NID of the
     OBJECT IDENTIFIER representing the given message digest when
     passed an EVP_MD structure.  For example
     EVP_MD_type(EVP_sha1()) returns NID_sha1. This function is
     normally used when setting ASN1 OIDs.

     EVP_MD_CTX_md() returns the EVP_MD structure corresponding
     to the passed EVP_MD_CTX.

     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
     NID_sha1WithRSAEncryption. Since digests and signature
     algorithms are no longer linked this function is only
     retained for compatibility reasons.

     EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_sha224(),
     EVP_sha256(), EVP_sha384(), EVP_sha512(), EVP_mdc2() and
     EVP_ripemd160() return EVP_MD structures for the MD2, MD5,
     SHA, SHA1, SHA224, SHA256, SHA384, SHA512, MDC2 and
     RIPEMD160 digest algorithms respectively.

     EVP_dss() and EVP_dss1() return EVP_MD structures for SHA
     and SHA1 digest algorithms but using DSS (DSA) for the
     signature algorithm. Note: there is no need to use these
     pseudo-digests in OpenSSL 1.0.0 and later, they are however

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EVP_DigestInit(3)            OpenSSL            EVP_DigestInit(3)

     retained for compatibility.

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

     EVP_get_digestbyname(), EVP_get_digestbynid() and
     EVP_get_digestbyobj() return an EVP_MD 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.


     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

     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() and
     EVP_MD_CTX_block_size() return the digest or block size in

     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 EVP_MD structure or
     NULL if an error occurs.


     The EVP 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.

     New applications should use the SHA2 digest algorithms such
     as SHA256.  The other digest algorithms are still in common

     For most applications the impl 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

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EVP_DigestInit(3)            OpenSSL            EVP_DigestInit(3)

     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.

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

     Stack allocation of EVP_MD_CTX structures is common, for

      EVP_MD_CTX mctx;

     This will cause binary compatibility issues if the size of
     EVP_MD_CTX structure changes (this will only happen with a
     major release of OpenSSL).  Applications wishing to avoid
     this should use EVP_MD_CTX_create() instead:

      EVP_MD_CTX *mctx;
      mctx = EVP_MD_CTX_create();


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

      #include <stdio.h>
      #include <openssl/evp.h>

      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;


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

      md = EVP_get_digestbyname(argv[1]);

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

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EVP_DigestInit(3)            OpenSSL            EVP_DigestInit(3)

      mdctx = EVP_MD_CTX_create();
      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);

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

      /* Call this once before exit. */


     dgst(1), evp(3)


     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 truly const EVP_MD * in OpenSSL 0.9.7.

     The link between digests and signing algorithms was fixed in
     OpenSSL 1.0 and later, so now EVP_sha1() can be used with
     RSA and DSA; there is no need to use EVP_dss1() any more.

     OpenSSL 1.0 and later does not include the MD2 digest
     algorithm in the default configuration due to its security

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