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authorbeck <>2000-03-19 11:13:58 +0000
committerbeck <>2000-03-19 11:13:58 +0000
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OpenSSL 0.9.5 merge
*warning* this bumps shared lib minors for libssl and libcrypto from 2.1 to 2.2 if you are using the ssl26 packages for ssh and other things to work you will need to get new ones (see ~beck/libsslsnap/<arch>) on cvs or ~beck/src-patent.tar.gz on cvs
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1=pod
2
3=head1 NAME
4
5EVP_EncryptInit, EVP_EncryptUpdate, EVP_EncryptFinal - EVP cipher routines
6
7=head1 SYNOPSIS
8
9 #include <openssl/evp.h>
10
11 void EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
12 unsigned char *key, unsigned char *iv);
13 void EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
14 int *outl, unsigned char *in, int inl);
15 void EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out,
16 int *outl);
17
18 void EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
19 unsigned char *key, unsigned char *iv);
20 void EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
21 int *outl, unsigned char *in, int inl);
22 int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
23 int *outl);
24
25 void EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
26 unsigned char *key, unsigned char *iv, int enc);
27 void EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out,
28 int *outl, unsigned char *in, int inl);
29 int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char *outm,
30 int *outl);
31
32 void EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
33
34 const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
35 #define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
36 #define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
37
38 #define EVP_CIPHER_nid(e) ((e)->nid)
39 #define EVP_CIPHER_block_size(e) ((e)->block_size)
40 #define EVP_CIPHER_key_length(e) ((e)->key_len)
41 #define EVP_CIPHER_iv_length(e) ((e)->iv_len)
42
43 int EVP_CIPHER_type(const EVP_CIPHER *ctx);
44 #define EVP_CIPHER_CTX_cipher(e) ((e)->cipher)
45 #define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid)
46 #define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size)
47 #define EVP_CIPHER_CTX_key_length(e) ((e)->cipher->key_len)
48 #define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len)
49 #define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
50
51 int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
52 int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE *type);
53
54=head1 DESCRIPTION
55
56The EVP cipher routines are a high level interface to certain
57symmetric ciphers.
58
59EVP_EncryptInit() initialises a cipher context B<ctx> for encryption
60with cipher B<type>. B<type> is normally supplied by a function such
61as EVP_des_cbc() . B<key> is the symmetric key to use and B<iv> is the
62IV to use (if necessary), the actual number of bytes used for the
63key and IV depends on the cipher. It is possible to set all parameters
64to NULL except B<type> in an initial call and supply the remaining
65parameters in subsequent calls. This is normally done when the
66EVP_CIPHER_asn1_to_param() function is called to set the cipher
67parameters from an ASN1 AlgorithmIdentifier and the key from a
68different source.
69
70EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
71writes the encrypted version to B<out>. This function can be called
72multiple times to encrypt successive blocks of data. The amount
73of data written depends on the block alignment of the encrypted data:
74as a result the amount of data written may be anything from zero bytes
75to (inl + cipher_block_size - 1) so B<outl> should contain sufficient
76room. The actual number of bytes written is placed in B<outl>.
77
78EVP_EncryptFinal() encrypts the "final" data, that is any data that
79remains in a partial block. It uses L<standard block padding|/NOTES> (aka PKCS
80padding). The encrypted final data is written to B<out> which should
81have sufficient space for one cipher block. The number of bytes written
82is placed in B<outl>. After this function is called the encryption operation
83is finished and no further calls to EVP_EncryptUpdate() should be made.
84
85EVP_DecryptInit(), EVP_DecryptUpdate() and EVP_DecryptFinal() are the
86corresponding decryption operations. EVP_DecryptFinal() will return an
87error code if the final block is not correctly formatted. The parameters
88and restrictions are identical to the encryption operations except that
89the decrypted data buffer B<out> passed to EVP_DecryptUpdate() should
90have sufficient room for (B<inl> + cipher_block_size) bytes unless the
91cipher block size is 1 in which case B<inl> bytes is sufficient.
92
93EVP_CipherInit(), EVP_CipherUpdate() and EVP_CipherFinal() are functions
94that can be used for decryption or encryption. The operation performed
95depends on the value of the B<enc> parameter. It should be set to 1 for
96encryption and 0 for decryption.
97
98EVP_CIPHER_CTX_cleanup() clears all information from a cipher context.
99It should be called after all operations using a cipher are complete
100so sensitive information does not remain in memory.
101
102EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
103return an EVP_CIPHER structure when passed a cipher name, a NID or an
104ASN1_OBJECT structure.
105
106EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID of a cipher when
107passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX> structure. The actual NID
108value is an internal value which may not have a corresponding OBJECT
109IDENTIFIER.
110
111EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
112length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
113structure. The constant B<EVP_MAX_KEY_LENGTH> is the maximum key length
114for all ciphers.
115
116EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
117length of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>.
118It will return zero if the cipher does not use an IV. The constant
119B<EVP_MAX_IV_LENGTH> is the maximum IV length for all ciphers.
120
121EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
122size of a cipher when passed an B<EVP_CIPHER> or B<EVP_CIPHER_CTX>
123structure. The constant B<EVP_MAX_IV_LENGTH> is also the maximum block
124length for all ciphers.
125
126EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the type of the passed
127cipher or context. This "type" is the actual NID of the cipher OBJECT
128IDENTIFIER as such it ignores the cipher parameters and 40 bit RC2 and
129128 bit RC2 have the same NID. If the cipher does not have an object
130identifier or does not have ASN1 support this function will return
131B<NID_undef>.
132
133EVP_CIPHER_CTX_cipher() returns the B<EVP_CIPHER> structure when passed
134an B<EVP_CIPHER_CTX> structure.
135
136EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier "parameter" based
137on the passed cipher. This will typically include any parameters and an
138IV. The cipher IV (if any) must be set when this call is made. This call
139should be made before the cipher is actually "used" (before any
140EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example). This function
141may fail if the cipher does not have any ASN1 support.
142
143EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN1
144AlgorithmIdentifier "parameter". The precise effect depends on the cipher
145In the case of RC2, for example, it will set the IV and effective key length.
146This function should be called after the base cipher type is set but before
147the key is set. For example EVP_CipherInit() will be called with the IV and
148key set to NULL, EVP_CIPHER_asn1_to_param() will be called and finally
149EVP_CipherInit() again with all parameters except the key set to NULL. It is
150possible for this function to fail if the cipher does not have any ASN1 support
151or the parameters cannot be set (for example the RC2 effective key length
152does not have an B<EVP_CIPHER> structure).
153
154=head1 RETURN VALUES
155
156EVP_EncryptInit(), EVP_EncryptUpdate() and EVP_EncryptFinal() do not return
157values.
158
159EVP_DecryptInit() and EVP_DecryptUpdate() do not return values.
160EVP_DecryptFinal() returns 0 if the decrypt failed or 1 for success.
161
162EVP_CipherInit() and EVP_CipherUpdate() do not return values.
163EVP_CipherFinal() returns 1 for a decryption failure or 1 for success, if
164the operation is encryption then it always returns 1.
165
166EVP_CIPHER_CTX_cleanup() does not return a value.
167
168EVP_get_cipherbyname(), EVP_get_cipherbynid() and EVP_get_cipherbyobj()
169return an B<EVP_CIPHER> structure or NULL on error.
170
171EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
172
173EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block
174size.
175
176EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length() return the key
177length.
178
179EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length() return the IV
180length or zero if the cipher does not use an IV.
181
182EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher's
183OBJECT IDENTIFIER or NID_undef if it has no defined OBJECT IDENTIFIER.
184
185EVP_CIPHER_CTX_cipher() returns an B<EVP_CIPHER> structure.
186
187EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return 1 for
188success or zero for failure.
189
190=head1 NOTES
191
192Where possible the B<EVP> interface to symmetric ciphers should be used in
193preference to the low level interfaces. This is because the code then becomes
194transparent to the cipher used and much more flexible.
195
196PKCS padding works by adding B<n> padding bytes of value B<n> to make the total
197length of the encrypted data a multiple of the block size. Padding is always
198added so if the data is already a multiple of the block size B<n> will equal
199the block size. For example if the block size is 8 and 11 bytes are to be
200encrypted then 5 padding bytes of value 5 will be added.
201
202When decrypting the final block is checked to see if it has the correct form.
203
204Although the decryption operation can produce an error, it is not a strong
205test that the input data or key is correct. A random block has better than
2061 in 256 chance of being of the correct format and problems with the
207input data earlier on will not produce a final decrypt error.
208
209=head1 BUGS
210
211The current B<EVP> cipher interface is not as flexible as it should be. Only
212certain "spot" encryption algorithms can be used for ciphers which have various
213parameters associated with them (RC2, RC5 for example) this is inadequate.
214
215Several of the functions do not return error codes because the software versions
216can never fail. This is not true of hardware versions.
217
218=head1 SEE ALSO
219
220L<evp(3)|evp(3)>
221
222=head1 HISTORY
223
224=cut