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| EVP_DIGESTINIT(3) | Library Functions Manual | EVP_DIGESTINIT(3) |
NAME
EVP_MD_CTX_new,
EVP_MD_CTX_reset,
EVP_MD_CTX_free,
EVP_MD_CTX_init,
EVP_MD_CTX_create,
EVP_MD_CTX_cleanup,
EVP_MD_CTX_destroy,
EVP_MD_CTX_ctrl,
EVP_DigestInit_ex,
EVP_DigestUpdate,
EVP_DigestFinal_ex,
EVP_Digest,
EVP_MD_CTX_copy_ex,
EVP_DigestInit,
EVP_DigestFinal,
EVP_MD_CTX_copy,
EVP_MAX_MD_SIZE,
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_md5,
EVP_md5_sha1,
EVP_sha1,
EVP_sha224,
EVP_sha256,
EVP_sha384,
EVP_sha512,
EVP_ripemd160,
EVP_get_digestbyname,
EVP_get_digestbynid,
EVP_get_digestbyobj —
EVP digest routines
SYNOPSIS
#include
<openssl/evp.h>
EVP_MD_CTX *
EVP_MD_CTX_new(void);
int
EVP_MD_CTX_reset(EVP_MD_CTX
*ctx);
void
EVP_MD_CTX_free(EVP_MD_CTX
*ctx);
void
EVP_MD_CTX_init(EVP_MD_CTX
*ctx);
EVP_MD_CTX *
EVP_MD_CTX_create(void);
int
EVP_MD_CTX_cleanup(EVP_MD_CTX
*ctx);
void
EVP_MD_CTX_destroy(EVP_MD_CTX
*ctx);
int
EVP_MD_CTX_ctrl(EVP_MD_CTX
*ctx, int cmd,
int p1, void*
p2);
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_Digest(const
void *d, size_t cnt,
unsigned char *md,
unsigned int *s,
const EVP_MD *type,
ENGINE *impl);
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);
int
EVP_MD_CTX_size(const
EVP_MD *ctx);
int
EVP_MD_CTX_block_size(const
EVP_MD *ctx);
int
EVP_MD_CTX_type(const
EVP_MD *ctx);
const EVP_MD *
EVP_md_null(void);
const EVP_MD *
EVP_md5(void);
const EVP_MD *
EVP_md5_sha1(void);
const EVP_MD *
EVP_sha1(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_ripemd160(void);
const EVP_MD *
EVP_get_digestbyname(const
char *name);
const EVP_MD *
EVP_get_digestbynid(int
type);
const EVP_MD *
EVP_get_digestbyobj(const
ASN1_OBJECT *o);
DESCRIPTION
The EVP digest routines are a high level interface to message digests and should be used instead of the cipher-specific functions.EVP_MD_CTX_new() allocates a new, empty
digest context.
EVP_MD_CTX_reset() cleans up
ctx and resets it to the state it had after
EVP_MD_CTX_new(), such that it can be
reused.
EVP_MD_CTX_free() cleans up
ctx and frees the space allocated to it.
EVP_MD_CTX_init() is a deprecated function to
clear a digest context on the stack before use. Do not use it on a digest
context returned from EVP_MD_CTX_new() or
one that was already used.
EVP_MD_CTX_create(),
EVP_MD_CTX_cleanup(), and
EVP_MD_CTX_destroy() are deprecated aliases
for EVP_MD_CTX_new(),
EVP_MD_CTX_reset(), and
EVP_MD_CTX_free(), respectively.
EVP_MD_CTX_ctrl() performs digest-specific
control actions on the context ctx.
EVP_DigestInit_ex() sets up the digest
context ctx to use a digest
type from
ENGINE impl.
The type will typically be supplied by a
function such 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_Digest() is a simple wrapper function to
hash cnt bytes of data at
d using the digest
type from
ENGINE impl
in a one-shot operation and place the digest value into
md, and, unless
s is NULL,
the length of the digest in bytes into *s.
This wrapper uses a temporary digest context and passes its arguments to
EVP_DigestInit_ex(),
EVP_DigestUpdate(), and
EVP_DigestFinal_ex() internally.
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.
EVP_DigestInit() is a deprecated function
behaving like EVP_DigestInit_ex() except
that it always uses the default digest implementation and that it requires
EVP_MD_CTX_reset() before it can be used on
a context that was already used.
EVP_DigestFinal() is a deprecated function
behaving like EVP_DigestFinal_ex() except
that the digest context ctx is automatically
cleaned up after use by calling
EVP_MD_CTX_reset() internally.
EVP_MD_CTX_copy() is a deprecated function
behaving like EVP_MD_CTX_copy_ex() except
that it requires EVP_MD_CTX_reset() before
a context that was already used can be passed as
out.
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 ASN.1 OIDs.
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_md5(),
EVP_sha1(),
EVP_sha224(),
EVP_sha256(),
EVP_sha384(),
EVP_sha512(), and
EVP_ripemd160() return
EVP_MD structures for the MD5, SHA1, SHA224,
SHA256, SHA384, SHA512 and RIPEMD160 digest algorithms respectively.
EVP_md5_sha1() returns an
EVP_MD structure that provides concatenated
MD5 and SHA1 message digests.
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.
EVP_MD_CTX_size(),
EVP_MD_CTX_block_size(),
EVP_MD_CTX_type(),
EVP_get_digestbynid(), and
EVP_get_digestbyobj() are implemented as
macros.
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 use.
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
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.
If digest contexts are not cleaned up after use, memory leaks will occur.
RETURN VALUES
EVP_MD_CTX_new() and
EVP_MD_CTX_create() return the new
EVP_MD_CTX object or
NULL for failure.
EVP_MD_CTX_reset() and
EVP_MD_CTX_cleanup() always return 1.
EVP_MD_CTX_ctrl(),
EVP_DigestInit_ex(),
EVP_DigestUpdate(),
EVP_DigestFinal_ex(),
EVP_Digest(),
EVP_MD_CTX_copy_ex(),
EVP_DigestInit(),
EVP_DigestFinal(), and
EVP_MD_CTX_copy() return 1 for success or 0
for failure.
EVP_MD_type(),
EVP_MD_pkey_type(), and
EVP_MD_CTX_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 bytes.
EVP_MD_CTX_md() returns the
EVP_MD object used by
ctx, or
NULL if
ctx is
NULL.
EVP_md_null(),
EVP_md5(),
EVP_md5_sha1(),
EVP_sha1(), 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.
EXAMPLES
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>
int
main(int argc, char *argv[])
{
EVP_MD_CTX *mdctx;
const EVP_MD *md;
const char mess1[] = "Test Message\n";
const char mess2[] = "Hello World\n";
unsigned char md_value[EVP_MAX_MD_SIZE];
int md_len, i;
if (argc <= 1) {
printf("Usage: mdtest digestname\n");
exit(1);
}
md = EVP_get_digestbyname(argv[1]);
if (md == NULL) {
printf("Unknown message digest %s\n", argv[1]);
exit(1);
}
mdctx = EVP_MD_CTX_new();
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_free(mdctx);
printf("Digest is: ");
for(i = 0; i < md_len; i++)
printf("%02x", md_value[i]);
printf("\n");
return 0;
}
SEE ALSO
BIO_f_md(3), CMAC_Init(3), evp(3), EVP_BytesToKey(3), EVP_DigestSignInit(3), EVP_DigestVerifyInit(3), EVP_PKEY_CTX_set_signature_md(3), EVP_PKEY_meth_set_signctx(3), EVP_SignInit(3), EVP_sm3(3), EVP_VerifyInit(3), EVP_whirlpool(3), HMAC(3), OCSP_basic_sign(3), OCSP_request_sign(3), PKCS5_PBKDF2_HMAC(3), PKCS7_sign_add_signer(3), X509_ALGOR_set_md(3), X509_digest(3), X509_sign(3)HISTORY
EVP_DigestInit(),
EVP_DigestUpdate(),
EVP_DigestFinal(),
EVP_MAX_MD_SIZE,
EVP_md5(), and
EVP_sha1() first appeared in SSLeay 0.5.1.
EVP_MD_size() first appeared in SSLeay
0.6.6. EVP_MD_CTX_size(),
EVP_MD_CTX_type(),
EVP_md_null(), and
EVP_get_digestbyname() first appeared in
SSLeay 0.8.0. EVP_MD_type(),
EVP_MD_pkey_type(),
EVP_get_digestbynid(), and
EVP_get_digestbyobj() first appeared in
SSLeay 0.8.1. EVP_MD_block_size(),
EVP_MD_CTX_size(),
EVP_MD_CTX_block_size(),
EVP_rc4_40(),
EVP_rc2_40_cbc(), and
EVP_ripemd160() first appeared in SSLeay
0.9.0. All these functions have been available since OpenBSD
2.4.
EVP_MD_CTX_copy() first appeared in OpenSSL
0.9.2b and has been available since OpenBSD 2.6.
EVP_MD_CTX_md() first appeared in OpenSSL
0.9.5 and has been available since OpenBSD 2.7.
EVP_MD_CTX_init(),
EVP_MD_CTX_create(),
EVP_MD_CTX_cleanup(),
EVP_MD_CTX_destroy(),
EVP_DigestInit_ex(),
EVP_DigestFinal_ex(),
EVP_Digest(), and
EVP_MD_CTX_copy_ex() first appeared in
OpenSSL 0.9.7 and have been available since OpenBSD
3.2.
EVP_sha224(),
EVP_sha256(),
EVP_sha384(), and
EVP_sha512() first appeared in OpenSSL
0.9.7h and 0.9.8a and have been available since OpenBSD
4.0.
EVP_MD_CTX_ctrl() first appeared in OpenSSL
1.1.0 and has been available since OpenBSD 5.7.
EVP_MD_CTX_new(),
EVP_MD_CTX_reset(),
EVP_MD_CTX_free(), and
EVP_md5_sha1() first appeared in OpenSSL
1.1.0 and have been available since OpenBSD 6.3.
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.| August 31, 2022 | Debian |