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EVP_DIGESTINIT(3)
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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
#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, unsigned int 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)
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))
The EVP digest routines are a high level interface to message
digests.
EVP_MD_CTX_init() initializes digest contet ctx.
EVP_MD_CTX_create() allocates, initializes and returns a
digest contet.
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_DigestUp-
date() 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 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_Diges-
tInit_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 contet 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. 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 EVP_MD 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 EVP_MD 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.
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_DigestFi-
nal_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 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.
SHA1 is the digest of choice for new applications. The
other digest algorithms are still in common use.
For most applications the impl parameter to EVP_Diges-
tInit_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.
In OpenSSL 0.9.7 and later if digest contexts are not
cleaned up after use memory leaks will occur. This example digests the data "Test Message0 and "Hello
World0, 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 Message0;
char mess2[] = "Hello World0;
unsigned char md_value[EVP_MAX_MD_SIZE];
int md_len, i;
OpenSSL_add_all_digests();
if(!argv[1]) {
printf("Usage: mdtest digestname0);
exit(1);
}
md = EVP_get_digestbyname(argv[1]);
if(!md) {
printf("Unknown message digest %s0, 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("0);
}
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.
evp(3), HMAC(3), MD2(3), MD5(3), MDC2(3), RIPEMD160(3),
SHA1(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_Digest-
Final_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.
OpenBSD 3.6 2004-04-08 6 [ Back ] |
