5 EVP_DigestInit, EVP_DigestUpdate, EVP_DigestFinal - EVP digest routines
9 #include <openssl/evp.h>
11 void EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
12 void EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
13 void EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
16 #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
18 int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);
20 #define EVP_MD_type(e) ((e)->type)
21 #define EVP_MD_pkey_type(e) ((e)->pkey_type)
22 #define EVP_MD_size(e) ((e)->md_size)
23 #define EVP_MD_block_size(e) ((e)->block_size)
25 #define EVP_MD_CTX_md(e) (e)->digest)
26 #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest)
27 #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest)
28 #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest)
30 EVP_MD *EVP_md_null(void);
31 EVP_MD *EVP_md2(void);
32 EVP_MD *EVP_md5(void);
33 EVP_MD *EVP_sha(void);
34 EVP_MD *EVP_sha1(void);
35 EVP_MD *EVP_dss(void);
36 EVP_MD *EVP_dss1(void);
37 EVP_MD *EVP_mdc2(void);
38 EVP_MD *EVP_ripemd160(void);
40 const EVP_MD *EVP_get_digestbyname(const char *name);
41 #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
42 #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))
46 The EVP digest routines are a high level interface to message digests.
48 EVP_DigestInit() initialises a digest context B<ctx> to use a digest
49 B<type>: this will typically be supplied by a function such as
52 EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the
53 digest context B<ctx>. This funtion can be called several times on the
54 same B<ctx> to hash additional data.
56 EVP_DigestFinal() retrieves the digest value from B<ctx> and places
57 it in B<md>. If the B<s> parameter is not NULL then the number of
58 bytes of data written (i.e. the length of the digest) will be written
59 to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.
60 After calling EVP_DigestFinal() no additional calls to EVP_DigestUpdate()
61 can be made, but EVP_DigestInit() can be called to initialiase a new
64 EVP_MD_CTX_copy() can be used to copy the message digest state from
65 B<in> to B<out>. This is useful if large amounts of data are to be
66 hashed which only differ in the last few bytes.
68 EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest
69 when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the
72 EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the
73 message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure.
75 EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER
76 representing the given message digest when passed an B<EVP_MD> structure.
77 For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is
78 normally used when setting ASN1 OIDs.
80 EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed
83 EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated
84 with this digest. For example EVP_sha1() is associated with RSA so this will
85 return B<NID_sha1WithRSAEncryption>. This "link" between digests and signature
86 algorithms may not be retained in future versions of OpenSSL.
88 EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and EVP_ripemd160()
89 return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest
90 algorithms respectively. The associated signature algorithm is RSA in each case.
92 EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest
93 algorithms but using DSS (DSA) for the signature algorithm.
95 EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it
96 returns is of zero length.
98 EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
99 return an B<EVP_MD> structure when passed a digest name, a digest NID or
100 an ASN1_OBJECT structure respectively. The digest table must be initialised
101 using, for example, OpenSSL_add_all_digests() for these functions to work.
105 EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() do not return values.
107 EVP_MD_CTX_copy() returns 1 if successful or 0 for failure.
109 EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the
110 corresponding OBJECT IDENTIFIER or NID_undef if none exists.
112 EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e), EVP_MD_size(),
113 EVP_MD_CTX_block_size() and EVP_MD_block_size() return the digest or block
116 EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(),
117 EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the
118 corresponding EVP_MD structures.
120 EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
121 return either an B<EVP_MD> structure or NULL if an error occurs.
125 The B<EVP> interface to message digests should almost always be used in
126 preference to the low level interfaces. This is because the code then becomes
127 transparent to the digest used and much more flexible.
129 SHA1 is the digest of choice for new applications. The other digest algorithms
130 are still in common use.
134 This example digests the data "Test Message\n" and "Hello World\n", using the
135 digest name passed on the command line.
138 #include <openssl/evp.h>
140 main(int argc, char *argv[])
144 char mess1[] = "Test Message\n";
145 char mess2[] = "Hello World\n";
146 unsigned char md_value[EVP_MAX_MD_SIZE];
149 OpenSSL_add_all_digests();
152 printf("Usage: mdtest digestname\n");
156 md = EVP_get_digestbyname(argv[1]);
159 printf("Unknown message digest %s\n", argv[1]);
163 EVP_DigestInit(&mdctx, md);
164 EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
165 EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
166 EVP_DigestFinal(&mdctx, md_value, &md_len);
168 printf("Digest is: ");
169 for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
175 Several of the functions do not return values: maybe they should. Although the
176 internal digest operations will never fail some future hardware based operations
179 The link between digests and signing algorithms results in a situation where
180 EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS
181 even though they are identical digests.
183 The size of an B<EVP_MD_CTX> structure is determined at compile time: this results
184 in code that must be recompiled if the size of B<EVP_MD_CTX> increases.
188 L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
189 L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>,
190 L<sha(3)|sha(3)>, L<digest(1)|digest(1)>
194 EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are
195 available in all versions of SSLeay and OpenSSL.