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EVP_ENCRYPTINIT(3)
Contents
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EVP_CIPHER_CTX_init, EVP_EncryptInit_ex, EVP_EncryptUpdate,
EVP_EncryptFinal_ex, EVP_DecryptInit_ex, EVP_DecryptUpdate,
EVP_DecryptFinal_ex, EVP_CipherInit_ex,
EVP_CipherUpdate, EVP_CipherFinal_ex,
EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl,
EVP_CIPHER_CTX_cleanup, EVP_EncryptInit, EVP_EncryptFinal,
EVP_DecryptInit, EVP_DecryptFinal, EVP_CipherInit,
EVP_CipherFinal, EVP_get_cipherbyname, EVP_get_cipherbynid,
EVP_get_cipherbyobj, EVP_CIPHER_nid,
EVP_CIPHER_block_size, EVP_CIPHER_key_length,
EVP_CIPHER_iv_length, EVP_CIPHER_flags, EVP_CIPHER_mode,
EVP_CIPHER_type, EVP_CIPHER_CTX_cipher,
EVP_CIPHER_CTX_nid, EVP_CIPHER_CTX_block_size,
EVP_CIPHER_CTX_key_length, EVP_CIPHER_CTX_iv_length,
EVP_CIPHER_CTX_get_app_data, EVP_CIPHER_CTX_set_app_data,
EVP_CIPHER_CTX_type, EVP_CIPHER_CTX_flags,
EVP_CIPHER_CTX_mode, EVP_CIPHER_param_to_asn1,
EVP_CIPHER_asn1_to_param, EVP_CIPHER_CTX_set_padding - EVP
cipher routines
#include <openssl/evp.h>
int EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *a);
int EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, unsigned char *key, unsigned char
*iv);
int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char
*out,
int *outl, unsigned char *in, int inl);
int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned
char *out,
int *outl);
int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, unsigned char *key, unsigned char
*iv);
int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char
*out,
int *outl, unsigned char *in, int inl);
int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned
char *outm,
int *outl);
int EVP_CipherInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, unsigned char *key, unsigned char
*iv, int enc);
int EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char
*out,
int *outl, unsigned char *in, int inl);
int EVP_CipherFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char
*outm,
int *outl);
int EVP_EncryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER
*type,
unsigned char *key, unsigned char *iv);
int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char
*out,
int *outl);
int EVP_DecryptInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER
*type,
unsigned char *key, unsigned char *iv);
int EVP_DecryptFinal(EVP_CIPHER_CTX *ctx, unsigned char
*outm,
int *outl);
int EVP_CipherInit(EVP_CIPHER_CTX *ctx, const EVP_CIPHER
*type,
unsigned char *key, unsigned char *iv, int enc);
int EVP_CipherFinal(EVP_CIPHER_CTX *ctx, unsigned char
*outm,
int *outl);
int EVP_CIPHER_CTX_set_padding(EVP_CIPHER_CTX *x, int
padding);
int EVP_CIPHER_CTX_set_key_length(EVP_CIPHER_CTX *x, int
keylen);
int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type,
int arg, void *ptr);
int EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *a);
const EVP_CIPHER *EVP_get_cipherbyname(const char *name);
#define EVP_get_cipherbynid(a) EVP_get_cipherbyname(OBJ_nid2sn(a))
#define EVP_get_cipherbyobj(a) EVP_get_cipherbynid(OBJ_obj2nid(a))
#define EVP_CIPHER_nid(e) ((e)->nid)
#define EVP_CIPHER_block_size(e) ((e)->block_size)
#define EVP_CIPHER_key_length(e) ((e)->key_len)
#define EVP_CIPHER_iv_length(e)
((e)->iv_len)
#define EVP_CIPHER_flags(e) ((e)->flags)
#define EVP_CIPHER_mode(e) ((e)->flags) &
EVP_CIPH_MODE)
int EVP_CIPHER_type(const EVP_CIPHER *ctx);
#define EVP_CIPHER_CTX_cipher(e) ((e)->cipher)
#define EVP_CIPHER_CTX_nid(e) ((e)->cipher->nid)
#define EVP_CIPHER_CTX_block_size(e) ((e)->cipher->block_size)
#define EVP_CIPHER_CTX_key_length(e) ((e)->key_len)
#define EVP_CIPHER_CTX_iv_length(e) ((e)->cipher->iv_len)
#define EVP_CIPHER_CTX_get_app_data(e) ((e)->app_data)
#define EVP_CIPHER_CTX_set_app_data(e,d) ((e)->app_data=(char *)(d))
#define EVP_CIPHER_CTX_type(c) EVP_CIPHER_type(EVP_CIPHER_CTX_cipher(c))
#define EVP_CIPHER_CTX_flags(e) ((e)->cipher->flags)
#define EVP_CIPHER_CTX_mode(e) ((e)->cipher->flags & EVP_CIPH_MODE)
int EVP_CIPHER_param_to_asn1(EVP_CIPHER_CTX *c, ASN1_TYPE
*type);
int EVP_CIPHER_asn1_to_param(EVP_CIPHER_CTX *c, ASN1_TYPE
*type);
The EVP cipher routines are a high level interface to certain
symmetric ciphers.
EVP_CIPHER_CTX_init() initializes cipher contex ctx.
EVP_EncryptInit_ex() sets up cipher context ctx for
encryption with cipher type from ENGINE impl. ctx must be
initialized before calling this function. type is normally
supplied by a function such as EVP_des_cbc(). If impl is
NULL then the default implementation is used. key is the
symmetric key to use and iv is the IV to use (if necessary),
the actual number of bytes used for the key and IV
depends on the cipher. It is possible to set all parameters
to NULL except type in an initial call and supply the
remaining parameters in subsequent calls, all of which
have type set to NULL. This is done when the default
cipher parameters are not appropriate.
EVP_EncryptUpdate() encrypts inl bytes from the buffer in
and writes the encrypted version to out. This function can
be called multiple times to encrypt successive blocks of
data. The amount of data written depends on the block
alignment of the encrypted data: as a result the amount of
data written may be anything from zero bytes to (inl +
cipher_block_size - 1) so outl should contain sufficient
room. The actual number of bytes written is placed in
outl.
If padding is enabled (the default) then EVP_EncryptFi-
nal_ex() encrypts the "final" data, that is any data that
remains in a partial block. It uses standard block
padding (aka PKCS padding). The encrypted final data is
written to out which should have sufficient space for one
cipher block. The number of bytes written is placed in
outl. After this function is called the encryption operation
is finished and no further calls to EVP_EncryptUp-
date() should be made.
If padding is disabled then EVP_EncryptFinal_ex() will not
encrypt any more data and it will return an error if any
data remains in a partial block: that is if the total data
length is not a multiple of the block size.
EVP_DecryptInit_ex(), EVP_DecryptUpdate() and EVP_Decrypt-
Final_ex() are the corresponding decryption operations.
EVP_DecryptFinal() will return an error code if padding is
enabled and the final block is not correctly formatted.
The parameters and restrictions are identical to the
encryption operations except that if padding is enabled
the decrypted data buffer out passed to EVP_DecryptUp-
date() should have sufficient room for (inl +
cipher_block_size) bytes unless the cipher block size is 1
in which case inl bytes is sufficient.
EVP_CipherInit_ex(), EVP_CipherUpdate() and EVP_CipherFi-
nal_ex() are functions that can be used for decryption or
encryption. The operation performed depends on the value
of the enc parameter. It should be set to 1 for encryption,
0 for decryption and -1 to leave the value unchanged
(the actual value of 'enc' being supplied in a previous
call).
EVP_CIPHER_CTX_cleanup() clears all information from a
cipher context and free up any allocated memory associate
with it. It should be called after all operations using a
cipher are complete so sensitive information does not
remain in memory.
EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit()
behave in a similar way to EVP_EncryptInit_ex(),
EVP_DecryptInit_ex and EVP_CipherInit_ex() except the ctx
paramter does not need to be initialized and they always
use the default cipher implementation.
EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFi-
nal() behave in a similar way to EVP_EncryptFinal_ex(),
EVP_DecryptFinal_ex() and EVP_CipherFinal_ex() except ctx
is automatically cleaned up after the call.
EVP_get_cipherbyname(), EVP_get_cipherbynid() and
EVP_get_cipherbyobj() return an EVP_CIPHER structure when
passed a cipher name, a NID or an ASN1_OBJECT structure.
EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return the NID
of a cipher when passed an EVP_CIPHER or EVP_CIPHER_CTX
structure. The actual NID value is an internal value
which may not have a corresponding OBJECT IDENTIFIER.
EVP_CIPHER_CTX_set_padding() enables or disables padding.
By default encryption operations are padded using standard
block padding and the padding is checked and removed when
decrypting. If the pad parameter is zero then no padding
is performed, the total amount of data encrypted or
decrypted must then be a multiple of the block size or an
error will occur.
EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length()
return the key length of a cipher when passed an
EVP_CIPHER or EVP_CIPHER_CTX structure. The constant
EVP_MAX_KEY_LENGTH is the maximum key length for all
ciphers. Note: although EVP_CIPHER_key_length() is fixed
for a given cipher, the value of
EVP_CIPHER_CTX_key_length() may be different for variable
key length ciphers.
EVP_CIPHER_CTX_set_key_length() sets the key length of the
cipher ctx. If the cipher is a fixed length cipher then
attempting to set the key length to any value other than
the fixed value is an error.
EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length()
return the IV length of a cipher when passed an EVP_CIPHER
or EVP_CIPHER_CTX. It will return zero if the cipher does
not use an IV. The constant EVP_MAX_IV_LENGTH is the maximum
IV length for all ciphers.
EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size()
return the block size of a cipher when passed an
EVP_CIPHER or EVP_CIPHER_CTX structure. The constant
EVP_MAX_IV_LENGTH is also the maximum block length for all
ciphers.
EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the
type of the passed cipher or context. This "type" is the
actual NID of the cipher OBJECT IDENTIFIER as such it
ignores the cipher parameters and 40 bit RC2 and 128 bit
RC2 have the same NID. If the cipher does not have an
object identifier or does not have ASN1 support this function
will return NID_undef.
EVP_CIPHER_CTX_cipher() returns the EVP_CIPHER structure
when passed an EVP_CIPHER_CTX structure.
EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return the
block cipher mode: EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE,
EVP_CIPH_CFB_MODE or EVP_CIPH_OFB_MODE. If the cipher is a
stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
EVP_CIPHER_param_to_asn1() sets the AlgorithmIdentifier
"parameter" based on the passed cipher. This will typically
include any parameters and an IV. The cipher IV (if
any) must be set when this call is made. This call should
be made before the cipher is actually "used" (before any
EVP_EncryptUpdate(), EVP_DecryptUpdate() calls for example).
This function may fail if the cipher does not have
any ASN1 support.
EVP_CIPHER_asn1_to_param() sets the cipher parameters
based on an ASN1 AlgorithmIdentifier "parameter". The precise
effect depends on the cipher In the case of RC2, for
example, it will set the IV and effective key length.
This function should be called after the base cipher type
is set but before the key is set. For example
EVP_CipherInit() will be called with the IV and key set to
NULL, EVP_CIPHER_asn1_to_param() will be called and
finally EVP_CipherInit() again with all parameters except
the key set to NULL. It is possible for this function to
fail if the cipher does not have any ASN1 support or the
parameters cannot be set (for example the RC2 effective
key length is not supported.
EVP_CIPHER_CTX_ctrl() allows various cipher specific
parameters to be determined and set. Currently only the
RC2 effective key length and the number of rounds of RC5
can be set.
EVP_CIPHER_CTX_init, EVP_EncryptInit_ex(), EVP_EncryptUp-
date() and EVP_EncryptFinal_ex() return 1 for success and
0 for failure.
EVP_DecryptInit_ex() and EVP_DecryptUpdate() return 1 for
success and 0 for failure. EVP_DecryptFinal_ex() returns
0 if the decrypt failed or 1 for success.
EVP_CipherInit_ex() and EVP_CipherUpdate() return 1 for
success and 0 for failure. EVP_CipherFinal_ex() returns 0
for a decryption failure or 1 for success.
EVP_CIPHER_CTX_cleanup() returns 1 for success and 0 for
failure.
EVP_get_cipherbyname(), EVP_get_cipherbynid() and
EVP_get_cipherbyobj() return an EVP_CIPHER structure or
NULL on error.
EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return a NID.
EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size()
return the block size.
EVP_CIPHER_key_length() and EVP_CIPHER_CTX_key_length()
return the key length.
EVP_CIPHER_CTX_set_padding() always returns 1.
EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length()
return the IV length or zero if the cipher does not use an
IV.
EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID
of the cipher's OBJECT IDENTIFIER or NID_undef if it has
no defined OBJECT IDENTIFIER.
EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.
EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param()
return 1 for success or zero for failure.
All algorithms have a fixed key length unless otherwise
stated.
EVP_enc_null()
Null cipher: does nothing.
EVP_des_cbc(void), EVP_des_ecb(void), EVP_des_cfb(void),
EVP_des_ofb(void)
DES in CBC, ECB, CFB and OFB modes respectively.
EVP_des_ede_cbc(void), EVP_des_ede(),
EVP_des_ede_ofb(void), EVP_des_ede_cfb(void)
Two key triple DES in CBC, ECB, CFB and OFB modes
respectively.
EVP_des_ede3_cbc(void), EVP_des_ede3(),
EVP_des_ede3_ofb(void), EVP_des_ede3_cfb(void)
Three key triple DES in CBC, ECB, CFB and OFB modes
respectively.
EVP_desx_cbc(void)
DESX algorithm in CBC mode.
EVP_rc4(void)
RC4 stream cipher. This is a variable key length
cipher with default key length 128 bits.
EVP_rc4_40(void)
RC4 stream cipher with 40 bit key length. This is
obsolete and new code should use EVP_rc4() and the
EVP_CIPHER_CTX_set_key_length() function.
EVP_idea_cbc() EVP_idea_ecb(void), EVP_idea_cfb(void),
EVP_idea_ofb(void), EVP_idea_cbc(void)
IDEA encryption algorithm in CBC, ECB, CFB and OFB
modes respectively.
EVP_rc2_cbc(void), EVP_rc2_ecb(void), EVP_rc2_cfb(void),
EVP_rc2_ofb(void)
RC2 encryption algorithm in CBC, ECB, CFB and OFB
modes respectively. This is a variable key length
cipher with an additional parameter called "effective
key bits" or "effective key length". By default both
are set to 128 bits.
EVP_rc2_40_cbc(void), EVP_rc2_64_cbc(void)
RC2 algorithm in CBC mode with a default key length
and effective key length of 40 and 64 bits. These are
obsolete and new code should use EVP_rc2_cbc(),
EVP_CIPHER_CTX_set_key_length() and
EVP_CIPHER_CTX_ctrl() to set the key length and effective
key length.
EVP_bf_cbc(void), EVP_bf_ecb(void), EVP_bf_cfb(void),
EVP_bf_ofb(void);
Blowfish encryption algorithm in CBC, ECB, CFB and OFB
modes respectively. This is a variable key length
cipher.
EVP_cast5_cbc(void), EVP_cast5_ecb(void),
EVP_cast5_cfb(void), EVP_cast5_ofb(void)
CAST encryption algorithm in CBC, ECB, CFB and OFB
modes respectively. This is a variable key length
cipher.
EVP_rc5_32_12_16_cbc(void), EVP_rc5_32_12_16_ecb(void),
EVP_rc5_32_12_16_cfb(void), EVP_rc5_32_12_16_ofb(void)
RC5 encryption algorithm in CBC, ECB, CFB and OFB
modes respectively. This is a variable key length
cipher with an additional "number of rounds" parameter.
By default the key length is set to 128 bits and
12 rounds. Where possible the EVP interface to symmetric ciphers
should be used in preference to the low level interfaces.
This is because the code then becomes transparent to the
cipher used and much more flexible.
PKCS padding works by adding n padding bytes of value n to
make the total length of the encrypted data a multiple of
the block size. Padding is always added so if the data is
already a multiple of the block size n will equal the
block size. For example if the block size is 8 and 11
bytes are to be encrypted then 5 padding bytes of value 5
will be added.
When decrypting the final block is checked to see if it
has the correct form.
Although the decryption operation can produce an error if
padding is enabled, it is not a strong test that the input
data or key is correct. A random block has better than 1
in 256 chance of being of the correct format and problems
with the input data earlier on will not produce a final
decrypt error.
If padding is disabled then the decryption operation will
always succeed if the total amount of data decrypted is a
multiple of the block size.
The functions EVP_EncryptInit(), EVP_EncryptFinal(),
EVP_DecryptInit(), EVP_CipherInit() and EVP_CipherFinal()
are obsolete but are retained for compatibility with
existing code. New code should use EVP_EncryptInit_ex(),
EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(), EVP_Decrypt-
Final_ex(), EVP_CipherInit_ex() and EVP_CipherFinal_ex()
because they can reuse an existing context without allocating
and freeing it up on each call.
For RC5 the number of rounds can currently only be set to
8, 12 or 16. This is a limitation of the current RC5 code
rather than the EVP interface.
EVP_MAX_KEY_LENGTH and EVP_MAX_IV_LENGTH only refer to the
internal ciphers with default key lengths. If custom
ciphers exceed these values the results are unpredictable.
This is because it has become standard practice to define
a generic key as a fixed unsigned char array containing
EVP_MAX_KEY_LENGTH bytes.
The ASN1 code is incomplete (and sometimes inaccurate) it
has only been tested for certain common S/MIME ciphers
(RC2, DES, triple DES) in CBC mode. Get the number of rounds used in RC5:
int nrounds;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0,
&nrounds);
Get the RC2 effective key length:
int key_bits;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0,
&key_bits);
Set the number of rounds used in RC5:
int nrounds;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS,
nrounds, NULL);
Set the effective key length used in RC2:
int key_bits;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS,
key_bits, NULL);
Encrypt a string using blowfish:
int do_crypt(char *outfile)
{
unsigned char outbuf[1024];
int outlen, tmplen;
/* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] =
{0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
unsigned char iv[] = {1,2,3,4,5,6,7,8};
char intext[] = "Some Crypto Text";
EVP_CIPHER_CTX ctx;
FILE *out;
EVP_CIPHER_CTX_init(&ctx);
EVP_EncryptInit_ex(&ctx, EVP_bf_cbc(), NULL, key,
iv);
if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
{
/* Error */
return 0;
}
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal_ex(&ctx, outbuf + outlen,
&tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
EVP_CIPHER_CTX_cleanup(&ctx);
/* Need binary mode for fopen because encrypted
data is
* binary data. Also cannot use strlen() on it because
* it wont be null terminated and may contain embedded
* nulls.
*/
out = fopen(outfile, "wb");
fwrite(outbuf, 1, outlen, out);
fclose(out);
return 1;
}
The ciphertext from the above example can be decrypted
using the openssl utility with the command line:
S<openssl bf -in cipher.bin -K
000102030405060708090A0B0C0D0E0F -iv 0102030405060708 -d>
General encryption, decryption function example using FILE
I/O and RC2 with an 80 bit key:
int do_crypt(FILE *in, FILE *out, int do_encrypt)
{
/* Allow enough space in output buffer for additional block */
inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
int inlen, outlen;
/* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] = "0123456789";
unsigned char iv[] = "12345678";
/* Don't set key or IV because we will modify the
parameters */
EVP_CIPHER_CTX_init(&ctx);
EVP_CipherInit_ex(&ctx, EVP_rc2(), NULL, NULL,
NULL, do_encrypt);
EVP_CIPHER_CTX_set_key_length(&ctx, 10);
/* We finished modifying parameters so now we can
set key and IV */
EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv,
do_encrypt);
for(;;)
{
inlen = fread(inbuf, 1, 1024, in);
if(inlen <= 0) break;
if(!EVP_CipherUpdate(&ctx, outbuf,
&outlen, inbuf, inlen))
{
/* Error */
return 0;
}
fwrite(outbuf, 1, outlen, out);
}
if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
{
/* Error */
return 0;
}
fwrite(outbuf, 1, outlen, out);
EVP_CIPHER_CTX_cleanup(&ctx);
return 1;
}
evp(3)
EVP_CIPHER_CTX_init(), EVP_EncryptInit_ex(), EVP_Encrypt-
Final_ex(), EVP_DecryptInit_ex(), EVP_DecryptFinal_ex(),
EVP_CipherInit_ex(), EVP_CipherFinal_ex() and
EVP_CIPHER_CTX_set_padding() appeared in OpenSSL 0.9.7.
OpenBSD 3.6 2003-05-11 11 [ Back ] |
