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EVP_EncryptInit(3)
Contents
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EVP_EncryptInit, EVP_EncryptUpdate, EVP_EncryptFinal,
EVP_DecryptInit, EVP_DecryptUpdate, EVP_DecryptFinal,
EVP_CipherInit, EVP_CipherUpdate, EVP_CipherFinal,
EVP_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl,
EVP_CIPHER_CTX_cleanup, 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 routines
#include <openssl/evp.h>
int EVP_EncryptInit(
EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
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(
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_DecryptUpdate(
EVP_CIPHER_CTX *ctx, unsigned char *out,
int *outl, unsigned char *in, int inl ); 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_CipherUpdate(
EVP_CIPHER_CTX *ctx, unsigned char *out,
int *outl, unsigned char *in, int inl ); int EVP_CipherFinal(
EVP_CIPHER_CTX *ctx, unsigned char *outm,
int *outl ); 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.
The EVP_EncryptInit() function initializes a cipher context
ctx for encryption with cipher type. The type is
usually supplied by a function such as EVP_des_cbc().The
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.
The EVP_EncryptUpdate() function 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.
The EVP_EncryptFinal() function encrypts the final data,
that is any data that remains in a partial block. It uses
standard block padding (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_EncryptUpdate() should be made.
The EVP_DecryptInit(), EVP_DecryptUpdate(), and
EVP_DecryptFinal() functions are the corresponding decryption
operations. The EVP_DecryptFinal() function will
return an error code if the final block is not formatted
correctly. The parameters and restrictions are identical
to the encryption operations except that the decrypted
data buffer out passed to EVP_DecryptUpdate() should have
sufficient room for (inl + cipher_block_size) bytes unless
the cipher block size is 1 in which case inl bytes is sufficient.
The EVP_CipherInit(), EVP_CipherUpdate(), and EVP_CipherFinal()functions
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).
The EVP_CIPHER_CTX_cleanup() function clears all information
from a cipher context. It should be called after all
operations using a cipher are complete so sensitive information
does not remain in memory.
The EVP_get_cipherbyname(), EVP_get_cipherbynid(), and
EVP_get_cipherbyobj() functions return an EVP_CIPHER
structure when passed a cipher name, a NID or an
ASN1_OBJECT structure.
The EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() functions
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.
The EVP_CIPHER_key_length() and
EVP_CIPHER_CTX_key_length() function 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. Although the
EVP_CIPHER_key_length() function is fixed for a given
cipher, the value of the EVP_CIPHER_CTX_key_length() function
may be different for variable key length ciphers.
The EVP_CIPHER_CTX_set_key_length() function 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.
The EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length()
functions 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.
The EVP_CIPHER_block_size() and
EVP_CIPHER_CTX_block_size() functions 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.
The EVP_CIPHER_type() and EVP_CIPHER_CTX_type() functions
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.
The EVP_CIPHER_CTX_cipher() function returns the
EVP_CIPHER structure when passed an EVP_CIPHER_CTX structure.
The EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() functions
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.
The EVP_CIPHER_param_to_asn1() function sets the AlgorithmIdentifier
parameter based on the passed cipher. This
typically will 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() or EVP_DecryptUpdate()
calls, for example). This function may fail if the
cipher does not have any ASN1 support.
The EVP_CIPHER_asn1_to_param() function 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,
the EVP_CipherInit() function will be called with the IV
and key set to NULL. The EVP_CIPHER_asn1_to_param() function
will be called and finally the EVP_CipherInit() function.
All parameters except the key are 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).
The EVP_CIPHER_CTX_ctrl() function 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.
Cipher Listing [Toc] [Back]
All algorithms have a fixed key length unless otherwise
stated. Null cipher: does nothing. DES in CBC, ECB, CFB
and OFB modes respectively. Two key triple DES in CBC,
ECB, CFB and OFB modes respectively. Three key triple DES
in CBC, ECB, CFB and OFB modes respectively. DESX algorithm
in CBC mode. RC4 stream cipher. This is a variable
key length cipher with default key length 128 bits. RC4
stream cipher with 40 bit key length. This is obsolete and
new code should use the EVP_rc4()and the
EVP_CIPHER_CTX_set_key_length() functions. IDEA encryption
algorithm in CBC, ECB, CFB and OFB modes respectively.
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.
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 the EVP_rc2_cbc(),
EVP_CIPHER_CTX_set_key_length(), and EVP_CIPHER_CTX_ctrl()
functions to set the key length and effective key length.
Blowfish encryption algorithm in CBC, ECB, CFB and OFB
modes respectively. This is a variable key length cipher.
CAST encryption algorithm in CBC, ECB, CFB and OFB modes
respectively. This is a variable key length cipher. 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, it
is not a strong test that the input data or key is correct.
A random block has better than a 1-in- 256 chance of
being of the correct format. Problems with the input data
earlier on will not produce a final decrypt error.
The EVP_EncryptInit(), EVP_EncryptUpdate(), EVP_EncryptFinal(),
EVP_DecryptInit(), EVP_DecryptUpdate(),
EVP_CipherInit(), EVP_CipherUpdate(), and
EVP_CIPHER_CTX_cleanup() functions did not return errors
in OpenSSL version 0.9.5a or earlier. Software only versions
of encryption algorithms will never return error
codes for these functions, unless there is a programming
error (for example, an attempt to set the key before the
cipher is set in EVP_EncryptInit()).
For RC5 the number of rounds can be set only to 8, 12 or
16. This is a limitation of the current RC5 code rather
than the EVP interface.
It is not possible to disable PKCS padding.
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.
The EVP_EncryptInit(), EVP_EncryptUpdate(), and
EVP_EncryptFinal() functions return 1 for success and 0
for failure.
The EVP_DecryptInit() and EVP_DecryptUpdate() functions
return 1 for success and 0 for failure. The EVP_DecryptFinal()
function returns 0 if the decrypt failed or 1 for
success.
The EVP_CipherInit() and EVP_CipherUpdate() functions
return 1 for success and 0 for failure.
The EVP_CipherFinal() function returns 0 for a decryption
failure or 1 for success.
The EVP_CIPHER_CTX_cleanup() function returns 1 for success
and 0 for failure.
The EVP_get_cipherbyname(), EVP_get_cipherbynid(), and
EVP_get_cipherbyobj() functions return an EVP_CIPHER
structure or NULL on error.
The EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() functions
return a NID.
The EVP_CIPHER_block_size() and
EVP_CIPHER_CTX_block_size() functions return the block
size.
The EVP_CIPHER_key_length() and
EVP_CIPHER_CTX_key_length() functions return the key
length.
The EVP_CIPHER_iv_length() and EVP_CIPHER_CTX_iv_length()
functions return the IV length or zero if the cipher does
not use an IV.
The EVP_CIPHER_type() and EVP_CIPHER_CTX_type() functions
return the NID of the cipher's OBJECT IDENTIFIER or
NID_undef if it has no defined OBJECT IDENTIFIER.
The EVP_CIPHER_CTX_cipher() function returns an EVP_CIPHER
structure.
The EVP_CIPHER_param_to_asn1() and
EVP_CIPHER_asn1_to_param() functions return 1 for success
or zero for failure.
Get the number of rounds used in RC5:
int nrounds;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC5_ROUNDS, 0, &i);
Get the RC2 effective key length:
int key_bits;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GET_RC2_KEY_BITS, 0,
&i);
Set the number of rounds used in RC5:
int nrounds;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC5_ROUNDS, i,
NULL);
Set the number of rounds used in RC2:
int nrounds;
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, i,
NULL);
Functions: evp(3)
EVP_EncryptInit(3)
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