a528d4f0a9
If something was "present in all versions" of SSLeay, or if it was added to a version of SSLeay (and therefore predates OpenSSL), remove mention of it. Documentation history now starts with OpenSSL. Remove mention of all history before OpenSSL 0.9.8, inclusive. Remove all AUTHOR sections. Reviewed-by: Tim Hudson <tjh@openssl.org>
267 lines
9.4 KiB
Text
267 lines
9.4 KiB
Text
=pod
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=head1 NAME
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EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate,
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EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE,
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EVP_MD_CTX_copy_ex, EVP_DigestInit, EVP_DigestFinal, EVP_MD_CTX_copy, EVP_MD_type,
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EVP_MD_pkey_type, EVP_MD_size, EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size,
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EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_md_null, EVP_md2, EVP_md5, EVP_sha1,
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EVP_sha224, EVP_sha256, EVP_sha384, EVP_sha512, EVP_dss1, EVP_mdc2,
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EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj -
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EVP digest routines
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
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EVP_MD_CTX *EVP_MD_CTX_create(void);
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int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
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int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
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int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
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unsigned int *s);
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int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
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void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);
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int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);
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int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
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int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
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unsigned int *s);
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int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);
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#define EVP_MAX_MD_SIZE 64 /* SHA512 */
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int EVP_MD_type(const EVP_MD *md);
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int EVP_MD_pkey_type(const EVP_MD *md);
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int EVP_MD_size(const EVP_MD *md);
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int EVP_MD_block_size(const EVP_MD *md);
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const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
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#define EVP_MD_CTX_size(e) EVP_MD_size(EVP_MD_CTX_md(e))
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#define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest)
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#define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest)
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const EVP_MD *EVP_md_null(void);
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const EVP_MD *EVP_md2(void);
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const EVP_MD *EVP_md5(void);
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const EVP_MD *EVP_sha1(void);
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const EVP_MD *EVP_dss1(void);
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const EVP_MD *EVP_mdc2(void);
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const EVP_MD *EVP_ripemd160(void);
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const EVP_MD *EVP_sha224(void);
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const EVP_MD *EVP_sha256(void);
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const EVP_MD *EVP_sha384(void);
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const EVP_MD *EVP_sha512(void);
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const EVP_MD *EVP_get_digestbyname(const char *name);
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#define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
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#define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))
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=head1 DESCRIPTION
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The EVP digest routines are a high level interface to message digests,
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and should be used instead of the cipher-specific functions.
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EVP_MD_CTX_init() initializes digest context B<ctx>.
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EVP_MD_CTX_create() allocates, initializes and returns a digest context.
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EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest
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B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this
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function. B<type> will typically be supplied by a function such as EVP_sha1().
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If B<impl> is NULL then the default implementation of digest B<type> is used.
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EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the
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digest context B<ctx>. This function can be called several times on the
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same B<ctx> to hash additional data.
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EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places
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it in B<md>. If the B<s> parameter is not NULL then the number of
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bytes of data written (i.e. the length of the digest) will be written
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to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.
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After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate()
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can be made, but EVP_DigestInit_ex() can be called to initialize a new
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digest operation.
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EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called
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after a digest context is no longer needed.
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EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the
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space allocated to it, it should be called only on a context created
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using EVP_MD_CTX_create().
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EVP_MD_CTX_copy_ex() can be used to copy the message digest state from
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B<in> to B<out>. This is useful if large amounts of data are to be
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hashed which only differ in the last few bytes. B<out> must be initialized
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before calling this function.
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EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except
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the passed context B<ctx> does not have to be initialized, and it always
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uses the default digest implementation.
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EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest
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context B<ctx> is automatically cleaned up.
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EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination
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B<out> does not have to be initialized.
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EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest
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when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the
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hash.
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EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the
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message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure.
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EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER
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representing the given message digest when passed an B<EVP_MD> structure.
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For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is
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normally used when setting ASN1 OIDs.
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EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed
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B<EVP_MD_CTX>.
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EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated
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with this digest. For example EVP_sha1() is associated with RSA so this will
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return B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms
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are no longer linked this function is only retained for compatibility
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reasons.
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EVP_md2(), EVP_md5(), EVP_sha1(), EVP_sha224(), EVP_sha256(),
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EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<EVP_MD>
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structures for the MD2, MD5, SHA1, SHA224, SHA256, SHA384, SHA512, MDC2
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and RIPEMD160 digest algorithms respectively.
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EVP_dss1() returns B<EVP_MD> an structure the SHA1 digest
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algorithm but using DSS (DSA) for the signature algorithm. Note: there is
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no need to use these pseudo-digests in OpenSSL 1.0.0 and later, they are
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however retained for compatibility.
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EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it
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returns is of zero length.
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EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
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return an B<EVP_MD> structure when passed a digest name, a digest NID or
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an ASN1_OBJECT structure respectively. The digest table must be initialized
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using, for example, OpenSSL_add_all_digests() for these functions to work.
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=head1 RETURN VALUES
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EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for
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success and 0 for failure.
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EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure.
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EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the
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corresponding OBJECT IDENTIFIER or NID_undef if none exists.
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EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size() and
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EVP_MD_CTX_block_size() return the digest or block size in bytes.
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EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha1(),
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EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the
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corresponding EVP_MD structures.
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EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
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return either an B<EVP_MD> structure or NULL if an error occurs.
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=head1 NOTES
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The B<EVP> interface to message digests should almost always be used in
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preference to the low level interfaces. This is because the code then becomes
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transparent to the digest used and much more flexible.
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New applications should use the SHA2 digest algorithms such as SHA256.
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The other digest algorithms are still in common use.
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For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
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set to NULL to use the default digest implementation.
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The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are
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obsolete but are retained to maintain compatibility with existing code. New
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applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
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EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
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instead of initializing and cleaning it up on each call and allow non default
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implementations of digests to be specified.
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If digest contexts are not cleaned up after use
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memory leaks will occur.
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Stack allocation of EVP_MD_CTX structures is common, for example:
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EVP_MD_CTX mctx;
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EVP_MD_CTX_init(&mctx);
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This will cause binary compatibility issues if the size of EVP_MD_CTX
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structure changes (this will only happen with a major release of OpenSSL).
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Applications wishing to avoid this should use EVP_MD_CTX_create() instead:
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EVP_MD_CTX *mctx;
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mctx = EVP_MD_CTX_create();
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=head1 EXAMPLE
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This example digests the data "Test Message\n" and "Hello World\n", using the
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digest name passed on the command line.
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#include <stdio.h>
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#include <openssl/evp.h>
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main(int argc, char *argv[])
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{
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EVP_MD_CTX *mdctx;
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const EVP_MD *md;
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char mess1[] = "Test Message\n";
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char mess2[] = "Hello World\n";
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unsigned char md_value[EVP_MAX_MD_SIZE];
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int md_len, i;
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OpenSSL_add_all_digests();
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if(!argv[1]) {
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printf("Usage: mdtest digestname\n");
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exit(1);
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}
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md = EVP_get_digestbyname(argv[1]);
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if(!md) {
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printf("Unknown message digest %s\n", argv[1]);
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exit(1);
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}
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mdctx = EVP_MD_CTX_create();
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EVP_DigestInit_ex(mdctx, md, NULL);
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EVP_DigestUpdate(mdctx, mess1, strlen(mess1));
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EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
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EVP_DigestFinal_ex(mdctx, md_value, &md_len);
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EVP_MD_CTX_destroy(mdctx);
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printf("Digest is: ");
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for(i = 0; i < md_len; i++)
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printf("%02x", md_value[i]);
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printf("\n");
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/* Call this once before exit. */
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EVP_cleanup();
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exit(0);
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}
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=head1 SEE ALSO
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L<dgst(1)>,
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L<evp(3)>
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=head1 HISTORY
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The link between digests and signing algorithms was fixed in OpenSSL 1.0 and
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later, so now EVP_sha1() can be used with RSA and DSA; there is no need to
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use EVP_dss1() any more.
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=cut
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