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update rather ancient EVP digest documentation

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This commit is contained in:
Dr. Stephen Henson 2012-04-10 22:28:01 +00:00
parent b1fd0ccb38
commit 5a34fcd76e
1 changed files with 43 additions and 23 deletions
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66
doc/crypto/EVP_DigestInit.pod
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@ -6,7 +6,8 @@ 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_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
@ -33,16 +34,15 @@ EVP digest routines
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_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);
#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)
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)
@ -56,6 +56,11 @@ EVP digest routines
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))
@ -124,12 +129,14 @@ B<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 B<NID_sha1WithRSAEncryption>. This "link" between digests and signature
algorithms may not be retained in future versions of OpenSSL.
return B<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_mdc2() and EVP_ripemd160()
return B<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_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_sha224(), EVP_sha256(),
EVP_sha384(), EVP_sha512(), EVP_mdc2() and EVP_ripemd160() return B<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 B<EVP_MD> structures for SHA and SHA1 digest
algorithms but using DSS (DSA) for the signature algorithm. Note: there is
@ -171,8 +178,8 @@ The B<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.
New applications should use the SHA2 digest algorithms such as SHA256.
The other digest algorithms are still in common use.
For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
set to NULL to use the default digest implementation.
@ -187,6 +194,19 @@ 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 example:
EVP_MD_CTX mctx;
EVP_MD_CTX_init(&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();
=head1 EXAMPLE
This example digests the data "Test Message\n" and "Hello World\n", using the
@ -197,7 +217,7 @@ digest name passed on the command line.
main(int argc, char *argv[])
{
EVP_MD_CTX mdctx;
EVP_MD_CTX *mdctx;
const EVP_MD *md;
char mess1[] = "Test Message\n";
char mess2[] = "Hello World\n";
@ -218,12 +238,12 @@ digest name passed on the command line.
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);
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);
EVP_MD_CTX_destroy(mdctx);
printf("Digest is: ");
for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);