1EVP_DigestInit(3) OpenSSL EVP_DigestInit(3)
2
6 EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUp‐
7 date, EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy,
8 EVP_MAX_MD_SIZE, EVP_MD_CTX_copy_ex, EVP_MD_CTX_copy, EVP_MD_type,
9 EVP_MD_pkey_type, EVP_MD_size, EVP_MD_block_size, EVP_MD_CTX_md,
10 EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_md_null,
11 EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_dss, EVP_dss1, EVP_mdc2,
12 EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid,
13 EVP_get_digestbyobj - EVP digest routines
14
16 #include <openssl/evp.h>
17 void EVP_MD_CTX_init(EVP_MD_CTX *ctx);
19 EVP_MD_CTX *EVP_MD_CTX_create(void);
20 int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
22 int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
23 int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md,
24 unsigned int *s);
25 int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx);
27 void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx);
28 int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in);
30 int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
32 int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md,
33 unsigned int *s);
34 int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in);
36 #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */
38 #define EVP_MD_type(e) ((e)->type)
40 #define EVP_MD_pkey_type(e) ((e)->pkey_type)
41 #define EVP_MD_size(e) ((e)->md_size)
42 #define EVP_MD_block_size(e) ((e)->block_size)
43 #define EVP_MD_CTX_md(e) (e)->digest)
45 #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest)
46 #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest)
47 #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest)
48 const EVP_MD *EVP_md_null(void);
50 const EVP_MD *EVP_md2(void);
51 const EVP_MD *EVP_md5(void);
52 const EVP_MD *EVP_sha(void);
53 const EVP_MD *EVP_sha1(void);
54 const EVP_MD *EVP_dss(void);
55 const EVP_MD *EVP_dss1(void);
56 const EVP_MD *EVP_mdc2(void);
57 const EVP_MD *EVP_ripemd160(void);
58 const EVP_MD *EVP_get_digestbyname(const char *name);
60 #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a))
61 #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a))
62
64 The EVP digest routines are a high level interface to message digests.
65 EVP_MD_CTX_init() initializes digest contet ctx.
67 EVP_MD_CTX_create() allocates, initializes and returns a digest contet.
69 EVP_DigestInit_ex() sets up digest context ctx to use a digest type
71 from ENGINE impl. ctx must be initialized before calling this function.
72 type will typically be supplied by a functionsuch as EVP_sha1(). If
73 impl is NULL then the default implementation of digest type is used.
74 EVP_DigestUpdate() hashes cnt bytes of data at d into the digest con‐
76 text ctx. This function can be called several times on the same ctx to
77 hash additional data.
78 EVP_DigestFinal_ex() retrieves the digest value from ctx and places it
80 in md. If the s parameter is not NULL then the number of bytes of data
81 written (i.e. the length of the digest) will be written to the integer
82 at s, at most EVP_MAX_MD_SIZE bytes will be written. After calling
83 EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate() can be
84 made, but EVP_DigestInit_ex() can be called to initialize a new digest
85 operation.
86 EVP_MD_CTX_cleanup() cleans up digest context ctx, it should be called
88 after a digest context is no longer needed.
89 EVP_MD_CTX_destroy() cleans up digest context ctx and frees up the
91 space allocated to it, it should be called only on a context created
92 using EVP_MD_CTX_create().
93 EVP_MD_CTX_copy_ex() can be used to copy the message digest state from
95 in to out. This is useful if large amounts of data are to be hashed
96 which only differ in the last few bytes. out must be initialized before
97 calling this function.
98 EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except
100 the passed context ctx does not have to be initialized, and it always
101 uses the default digest implementation.
102 EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest
104 contet ctx is automatically cleaned up.
105 EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the desti‐
107 nation out does not have to be initialized.
108 EVP_MD_size() and EVP_MD_CTX_size() return the size of the message
110 digest when passed an EVP_MD or an EVP_MD_CTX structure, i.e. the size
111 of the hash.
112 EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size
114 of the message digest when passed an EVP_MD or an EVP_MD_CTX structure.
115 EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDEN‐
117 TIFIER representing the given message digest when passed an EVP_MD
118 structure. For example EVP_MD_type(EVP_sha1()) returns NID_sha1. This
119 function is normally used when setting ASN1 OIDs.
120 EVP_MD_CTX_md() returns the EVP_MD structure corresponding to the
122 passed EVP_MD_CTX.
123 EVP_MD_pkey_type() returns the NID of the public key signing algorithm
125 associated with this digest. For example EVP_sha1() is associated with
126 RSA so this will return NID_sha1WithRSAEncryption. This "link" between
127 digests and signature algorithms may not be retained in future versions
128 of OpenSSL.
129 EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and
131 EVP_ripemd160() return EVP_MD structures for the MD2, MD5, SHA, SHA1,
132 MDC2 and RIPEMD160 digest algorithms respectively. The associated sig‐
133 nature algorithm is RSA in each case.
134 EVP_dss() and EVP_dss1() return EVP_MD structures for SHA and SHA1
136 digest algorithms but using DSS (DSA) for the signature algorithm.
137 EVP_md_null() is a "null" message digest that does nothing: i.e. the
139 hash it returns is of zero length.
140 EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
142 return an EVP_MD structure when passed a digest name, a digest NID or
143 an ASN1_OBJECT structure respectively. The digest table must be ini‐
144 tialized using, for example, OpenSSL_add_all_digests() for these func‐
145 tions to work.
146
148 EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return
149 1 for success and 0 for failure.
150 EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure.
152 EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of
154 the corresponding OBJECT IDENTIFIER or NID_undef if none exists.
155 EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e), EVP_MD_size(),
157 EVP_MD_CTX_block_size() and EVP_MD_block_size() return the digest or
158 block size in bytes.
159 EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(),
161 EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the cor‐
162 responding EVP_MD structures.
163 EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()
165 return either an EVP_MD structure or NULL if an error occurs.
166
168 The EVP interface to message digests should almost always be used in
169 preference to the low level interfaces. This is because the code then
170 becomes transparent to the digest used and much more flexible.
171 SHA1 is the digest of choice for new applications. The other digest
173 algorithms are still in common use.
174 For most applications the impl parameter to EVP_DigestInit_ex() will be
176 set to NULL to use the default digest implementation.
177 The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy()
179 are obsolete but are retained to maintain compatibility with existing
180 code. New applications should use EVP_DigestInit_ex(), EVP_DigestFi‐
181 nal_ex() and EVP_MD_CTX_copy_ex() because they can efficiently reuse a
182 digest context instead of initializing and cleaning it up on each call
183 and allow non default implementations of digests to be specified.
184 In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after
186 use memory leaks will occur.
187
189 This example digests the data "Test Message\n" and "Hello World\n",
190 using the digest name passed on the command line.
191 #include <stdio.h>
193 #include <openssl/evp.h>
194 main(int argc, char *argv[])
196 {
197 EVP_MD_CTX mdctx;
198 const EVP_MD *md;
199 char mess1[] = "Test Message\n";
200 char mess2[] = "Hello World\n";
201 unsigned char md_value[EVP_MAX_MD_SIZE];
202 int md_len, i;
203 OpenSSL_add_all_digests();
205 if(!argv[1]) {
207 printf("Usage: mdtest digestname\n");
208 exit(1);
209 }
210 md = EVP_get_digestbyname(argv[1]);
212 if(!md) {
214 printf("Unknown message digest %s\n", argv[1]);
215 exit(1);
216 }
217 EVP_MD_CTX_init(&mdctx);
219 EVP_DigestInit_ex(&mdctx, md, NULL);
220 EVP_DigestUpdate(&mdctx, mess1, strlen(mess1));
221 EVP_DigestUpdate(&mdctx, mess2, strlen(mess2));
222 EVP_DigestFinal_ex(&mdctx, md_value, &md_len);
223 EVP_MD_CTX_cleanup(&mdctx);
224 printf("Digest is: ");
226 for(i = 0; i < md_len; i++) printf("%02x", md_value[i]);
227 printf("\n");
228 }
229
231 The link between digests and signing algorithms results in a situation
232 where EVP_sha1() must be used with RSA and EVP_dss1() must be used with
233 DSS even though they are identical digests.
234
236 evp(3), hmac(3), md2(3), md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)
237
239 EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are avail‐
240 able in all versions of SSLeay and OpenSSL.
241 EVP_MD_CTX_init(), EVP_MD_CTX_create(), EVP_MD_CTX_copy_ex(),
243 EVP_MD_CTX_cleanup(), EVP_MD_CTX_destroy(), EVP_DigestInit_ex() and
244 EVP_DigestFinal_ex() were added in OpenSSL 0.9.7.
245 EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(),
247 EVP_dss1(), EVP_mdc2() and EVP_ripemd160() were changed to return tru‐
248 ely const EVP_MD * in OpenSSL 0.9.7.
2490.9.8b 2004-05-20 EVP_DigestInit(3)