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EVP_DigestInit(3)
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EVP_DigestInit, EVP_DigestUpdate, EVP_DigestFinal,
EVP_MAX_MD_SIZE, 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_DigestInit(
EVP_MD_CTX *ctx, const EVP_MD *type ); void
EVP_DigestUpdate(
EVP_MD_CTX *ctx, const void *d, unsigned int cnt
); void EVP_DigestFinal(
EVP_MD_CTX *ctx, unsigned char *md,
unsigned int *s ); #define EVP_MAX_MD_SIZE (16+20) /* The
SSLv3 md5+sha1 type */
int EVP_MD_CTX_copy(
EVP_MD_CTX *out,EVP_MD_CTX *in ); #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)
EVP_MD *EVP_md_null(
void ); EVP_MD *EVP_md2(
void ); EVP_MD *EVP_md5(
void ); EVP_MD *EVP_sha(
void ); EVP_MD *EVP_sha1(
void ); EVP_MD *EVP_dss(
void ); EVP_MD *EVP_dss1(
void ); EVP_MD *EVP_mdc2(
void ); 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.
The EVP_DigestInit() function initializes a digest context
ctx to use a digest type. This will typically be supplied
by a function such as EVP_sha1().
The EVP_DigestUpdate() function 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.
The EVP_DigestFinal() function 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() no additional calls to EVP_DigestUpdate()
can be made, but EVP_DigestInit() can be called to
initialize a new digest operation.
The EVP_MD_CTX_copy() function can be used to copy the
message digest state from in to out. This is useful to
hash large amounts of data which only differ in the last
few bytes.
The EVP_MD_size() and EVP_MD_CTX_size() functions 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.
The EVP_MD_block_size() and EVP_MD_CTX_block_size() functions
return the block size of the message digest when
passed an EVP_MD or an EVP_MD_CTX structure.
The EVP_MD_type() and EVP_MD_CTX_type() functions 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.
The EVP_MD_CTX_md() function returns the EVP_MD structure
corresponding to the passed EVP_MD_CTX.
The EVP_MD_pkey_type() function 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.
The EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(),
EVP_mdc2(), and EVP_ripemd160() functions 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.
The EVP_dss() and EVP_dss1() functions return EVP_MD
structures for SHA and SHA1 digest algorithms but using
DSS (DSA) for the signature algorithm.
The EVP_md_null() function is a null message digest that
does nothing. The hash it returns is of zero length.
The EVP_get_digestbyname(), EVP_get_digestbynid(), and
EVP_get_digestbyobj() functions 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.
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.
Several of the functions do not return values. Although
the internal digest operations will never fail some future
hardware based operations might.
The link between digests and signing algorithms results in
a situation where the EVP_sha1() function must be used
with RSA, and the EVP_dss1() function must be used with
DSS even though they are identical digests.
The size of an EVP_MD_CTX structure is determined at compile
time. This results in code that must be recompiled if
the size of EVP_MD_CTX increases.
The EVP_DigestInit(), EVP_DigestUpdate(), and EVP_DigestFinal()
functions do not return values.
The EVP_MD_CTX_copy() function returns 1 if successful or
0 for failure.
The EVP_MD_type(), EVP_MD_pkey_type(), and EVP_MD_type()
functions return the NID of the corresponding OBJECT IDENTIFIER
or NID_undef if none exists.
The EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(),
EVP_MD_size(), EVP_MD_CTX_block_size(), and
EVP_MD_block_size() functions return the digest or block
size in bytes.
The EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(),
EVP_sha1(), EVP_dss(), EVP_dss1(), EVP_mdc2(), and
EVP_ripemd160() functions return pointers to the corresponding
EVP_MD structures.
The EVP_get_digestbyname(), EVP_get_digestbynid(), and
EVP_get_digestbyobj() functions return either an EVP_MD
structure or NULL if an error occurs.
The following 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;
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_DigestInit(&mdctx, md);
EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
EVP_DigestFinal(&mdctx, md_value, &md_len);
printf("Digest is: ");
for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
printf("\n");
}
EVP_DigestInit(), EVP_DigestUpdate(), and EVP_DigestFinal()
are available in all versions of SSLeay and OpenSSL.
Commands: dgst(1)
Functions: evp(3), hmac(3), md2(3), md5(3), mdc2(3),
ripemd(3), sha(3),
EVP_DigestInit(3)
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