DragonFly On-Line Manual Pages
EVP_ENCRYPTINIT(3) DragonFly Library Functions Manual EVP_ENCRYPTINIT(3)
NAME
EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, EVP_CIPHER_CTX_cleanup,
EVP_CIPHER_CTX_init, EVP_CIPHER_CTX_free, 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_EncryptInit, EVP_EncryptFinal,
EVP_DecryptInit, EVP_DecryptFinal, EVP_CipherInit, EVP_CipherFinal,
EVP_CIPHER_CTX_set_padding, EVP_CIPHER_CTX_set_key_length,
EVP_CIPHER_CTX_ctrl, EVP_CIPHER_CTX_rand_key, 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_iv, EVP_CIPHER_CTX_set_iv,
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_enc_null,
EVP_des_cbc, EVP_des_ecb, EVP_des_cfb, EVP_des_ofb, EVP_des_ede_cbc,
EVP_des_ede, EVP_des_ede_ofb, EVP_des_ede_cfb, EVP_des_ede3_cbc,
EVP_des_ede3, EVP_des_ede3_ofb, EVP_des_ede3_cfb, EVP_desx_cbc, EVP_rc4,
EVP_rc4_40, EVP_rc4_hmac_md5, EVP_idea_cbc, EVP_idea_ecb, EVP_idea_cfb,
EVP_idea_ofb, EVP_rc2_cbc, EVP_rc2_ecb, EVP_rc2_cfb, EVP_rc2_ofb,
EVP_rc2_40_cbc, EVP_rc2_64_cbc, EVP_bf_cbc, EVP_bf_ecb, EVP_bf_cfb,
EVP_bf_ofb, EVP_cast5_cbc, EVP_cast5_ecb, EVP_cast5_cfb, EVP_cast5_ofb,
EVP_aes_128_cbc, EVP_aes_128_ecb, EVP_aes_128_cfb, EVP_aes_128_ofb,
EVP_aes_192_cbc, EVP_aes_192_ecb, EVP_aes_192_cfb, EVP_aes_192_ofb,
EVP_aes_256_cbc, EVP_aes_256_ecb, EVP_aes_256_cfb, EVP_aes_256_ofb,
EVP_aes_128_gcm, EVP_aes_192_gcm, EVP_aes_256_gcm, EVP_aes_128_ccm,
EVP_aes_192_ccm, EVP_aes_256_ccm, EVP_aes_128_cbc_hmac_sha1,
EVP_aes_256_cbc_hmac_sha1, EVP_chacha20 -- EVP cipher routines
SYNOPSIS
#include <openssl/evp.h>
EVP_CIPHER_CTX *
EVP_CIPHER_CTX_new(void);
int
EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx);
int
EVP_CIPHER_CTX_cleanup(EVP_CIPHER_CTX *ctx);
void
EVP_CIPHER_CTX_init(EVP_CIPHER_CTX *ctx);
void
EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx);
int
EVP_EncryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *type,
ENGINE *impl, const unsigned char *key, const unsigned char *iv);
int
EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
const 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, const unsigned char *key, const unsigned char *iv);
int
EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
const 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, const unsigned char *key, const unsigned char *iv,
int enc);
int
EVP_CipherUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
const 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,
const unsigned char *key, const 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,
const unsigned char *key, const 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,
const unsigned char *key, const 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_rand_key(EVP_CIPHER_CTX *ctx, unsigned char *key);
const EVP_CIPHER *
EVP_get_cipherbyname(const char *name);
const EVP_CIPHER *
EVP_get_cipherbynid(int nid);
const EVP_CIPHER *
EVP_get_cipherbyobj(const ASN1_OBJECT *a);
int
EVP_CIPHER_nid(const EVP_CIPHER *e);
int
EVP_CIPHER_block_size(const EVP_CIPHER *e);
int
EVP_CIPHER_key_length(const EVP_CIPHER *e);
int
EVP_CIPHER_iv_length(const EVP_CIPHER *e);
unsigned long
EVP_CIPHER_flags(const EVP_CIPHER *e);
unsigned long
EVP_CIPHER_mode(const EVP_CIPHER *e);
int
EVP_CIPHER_type(const EVP_CIPHER *ctx);
const EVP_CIPHER *
EVP_CIPHER_CTX_cipher(const EVP_CIPHER_CTX *ctx);
int
EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);
int
EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);
int
EVP_CIPHER_CTX_key_length(const EVP_CIPHER_CTX *ctx);
int
EVP_CIPHER_CTX_iv_length(const EVP_CIPHER_CTX *ctx);
int
EVP_CIPHER_CTX_get_iv(const EVP_CIPHER_CTX *ctx, u_char *iv, size_t len);
int
EVP_CIPHER_CTX_set_iv(EVP_CIPHER_CTX *ctx, const u_char *iv, size_t len);
void *
EVP_CIPHER_CTX_get_app_data(const EVP_CIPHER_CTX *ctx);
void
EVP_CIPHER_CTX_set_app_data(const EVP_CIPHER_CTX *ctx, void *data);
int
EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);
unsigned long
EVP_CIPHER_CTX_flags(const EVP_CIPHER_CTX *ctx);
unsigned long
EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);
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);
DESCRIPTION
The EVP cipher routines are a high level interface to certain symmetric
ciphers.
EVP_CIPHER_CTX_new() creates a new, empty cipher context.
EVP_CIPHER_CTX_reset() clears all information from ctx and frees all
allocated memory associated with it, except the ctx object itself, such
that it can be reused for another series of calls to EVP_CipherInit(),
EVP_CipherUpdate(), and EVP_CipherFinal(). It is also suitable for
cipher contexts on the stack that were used and are no longer needed.
EVP_CIPHER_CTX_cleanup() is a deprecated alias for
EVP_CIPHER_CTX_reset().
EVP_CIPHER_CTX_init() is a deprecated function to clear a cipher context
on the stack before use. Do not use it on a cipher context returned from
EVP_CIPHER_CTX_new() or one one that was already used.
EVP_CIPHER_CTX_free() clears all information from ctx and frees all allo-
cated memory associated with it, including ctx itself. This function
should be called after all operations using a cipher are complete, so
sensitive information does not remain in memory. If ctx is a NULL
pointer, no action occurs.
EVP_EncryptInit_ex() sets up the cipher context ctx for encryption with
cipher type from ENGINE impl. If ctx points to an unused object on the
stack, it must be initialized with EVP_MD_CTX_init() before calling this
function. type is normally supplied by a function such as
EVP_aes_256_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 neces-
sary). 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 out should contain sufficient room. The actual number of bytes writ-
ten is placed in outl.
If padding is enabled (the default) then EVP_EncryptFinal_ex() encrypts
the "final" data, that is any data that remains in a partial block. It
uses NOTES (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_EncryptUpdate() 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_DecryptFinal_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 encryp-
tion operations except that if padding is enabled the decrypted data buf-
fer 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.
EVP_CipherInit_ex(), EVP_CipherUpdate(), and EVP_CipherFinal_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_EncryptInit(), EVP_DecryptInit(), and EVP_CipherInit() are deprecated
functions behaving like EVP_EncryptInit_ex(), EVP_DecryptInit_ex(), and
EVP_CipherInit_ex() except that they always use the default cipher imple-
mentation and that they require EVP_CIPHER_CTX_reset() before they can be
used on a context that was already used.
EVP_EncryptFinal(), EVP_DecryptFinal(), and EVP_CipherFinal() are identi-
cal to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex(), and
EVP_CipherFinal_ex(). In previous releases of OpenSSL, they also used to
clean up the ctx, but this is no longer done and EVP_CIPHER_CTX_reset()
or EVP_CIPHER_CTX_free() must be called to free any context resources.
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 IDENTI-
FIER.
EVP_CIPHER_CTX_set_padding() enables or disables padding. This function
should be called after the context is set up for encryption or decryption
with EVP_EncryptInit_ex(), EVP_DecryptInit_ex(), or EVP_CipherInit_ex .
By default encryption operations are padded using standard block padding
and the padding is checked and removed when decrypting. If the padding
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_CTX_get_iv() and EVP_CIPHER_CTX_set_iv() will respectively
retrieve and set the IV for an EVP_CIPHER_CTX. In both cases, the speci-
fied IV length must exactly equal the expected IV length for the context
as returned by EVP_CIPHER_CTX_iv_length().
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_BLOCK_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 ASN.1 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,
EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, or EVP_CIPH_XTS_MODE. If the
cipher is a stream cipher then EVP_CIPH_STREAM_CIPHER is returned.
EVP_CIPHER_param_to_asn1() sets the ASN.1 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() or EVP_DecryptUpdate() calls, for example). This
function may fail if the cipher does not have any ASN.1 support.
EVP_CIPHER_asn1_to_param() sets the cipher parameters based on an ASN.1
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 ASN.1 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 can be
set.
EVP_CIPHER_CTX_rand_key() generates a random key of the appropriate
length based on the cipher context. The EVP_CIPHER can provide its own
random key generation routine to support keys of a specific form. The
key argument must point to a buffer at least as big as the value returned
by EVP_CIPHER_CTX_key_length().
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_DecryptFinal_ex(), EVP_CipherInit_ex(), and EVP_CipherFinal_ex()
because they can reuse an existing context without allocating and freeing
it up on each call.
EVP_get_cipherbynid() and EVP_get_cipherbyobj() are implemented as
macros.
RETURN VALUES
EVP_CIPHER_CTX_new() returns a pointer to a newly created EVP_CIPHER_CTX
for success or NULL for failure.
EVP_CIPHER_CTX_reset(), EVP_CIPHER_CTX_cleanup(),
EVP_CIPHER_CTX_get_iv(), EVP_CIPHER_CTX_set_iv(), 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_EncryptInit(),
EVP_EncryptFinal(), EVP_DecryptInit(), EVP_DecryptFinal(),
EVP_CipherInit(), EVP_CipherFinal(), EVP_CIPHER_CTX_set_key_length(), and
EVP_CIPHER_CTX_rand_key() return 1 for success or 0 for failure.
EVP_CIPHER_CTX_set_padding() always returns 1.
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_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 IDEN-
TIFIER.
EVP_CIPHER_CTX_cipher() returns an EVP_CIPHER structure.
EVP_CIPHER_param_to_asn1() and EVP_CIPHER_asn1_to_param() return greater
than zero for success and zero or a negative number for failure.
CIPHER LISTING
All algorithms have a fixed key length unless otherwise stated.
EVP_enc_null()
Null cipher: does nothing.
EVP_aes_128_cbc(), EVP_aes_128_ecb(), EVP_aes_128_cfb(),
EVP_aes_128_ofb()
AES with a 128-bit key in CBC, ECB, CFB and OFB modes respec-
tively.
EVP_aes_192_cbc(), EVP_aes_192_ecb(), EVP_aes_192_cfb(),
EVP_aes_192_ofb()
AES with a 192-bit key in CBC, ECB, CFB and OFB modes respec-
tively.
EVP_aes_256_cbc(), EVP_aes_256_ecb(), EVP_aes_256_cfb(),
EVP_aes_256_ofb()
AES with a 256-bit key in CBC, ECB, CFB and OFB modes respec-
tively.
EVP_des_cbc(), EVP_des_ecb(), EVP_des_cfb(), EVP_des_ofb()
DES in CBC, ECB, CFB and OFB modes respectively.
EVP_des_ede_cbc(), EVP_des_ede(), EVP_des_ede_ofb(), EVP_des_ede_cfb()
Two key triple DES in CBC, ECB, CFB and OFB modes respectively.
EVP_des_ede3_cbc(), EVP_des_ede3(), EVP_des_ede3_ofb(),
EVP_des_ede3_cfb()
Three key triple DES in CBC, ECB, CFB and OFB modes respectively.
EVP_desx_cbc()
DESX algorithm in CBC mode.
EVP_rc4()
RC4 stream cipher. This is a variable key length cipher with
default key length 128 bits.
EVP_rc4_40()
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(), EVP_idea_cfb(), EVP_idea_ofb()
IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respec-
tively.
EVP_rc2_cbc(), EVP_rc2_ecb(), EVP_rc2_cfb(), EVP_rc2_ofb()
RC2 encryption algorithm in CBC, ECB, CFB and OFB modes respec-
tively. 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(), EVP_rc2_64_cbc()
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(), EVP_bf_ecb(), EVP_bf_cfb(), EVP_bf_ofb()
Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes
respectively. This is a variable key length cipher.
EVP_cast5_cbc(), EVP_cast5_ecb(), EVP_cast5_cfb(), EVP_cast5_ofb()
CAST encryption algorithm in CBC, ECB, CFB and OFB modes respec-
tively. This is a variable key length cipher.
EVP_aes_128_gcm(), EVP_aes_192_gcm(), EVP_aes_256_gcm()
AES Galois Counter Mode (GCM) for 128, 192 and 256 bit keys
respectively. These ciphers require additional control opera-
tions to function correctly: see the GCM mode section below for
details.
EVP_aes_128_ccm(), EVP_aes_192_ccm(), EVP_aes_256_ccm()
AES Counter with CBC-MAC Mode (CCM) for 128, 192 and 256 bit keys
respectively. These ciphers require additional control opera-
tions to function correctly: see CCM mode section below for
details.
EVP_chacha20()
The ChaCha20 stream cipher. The key length is 256 bits, the IV
is 96 bits long.
GCM mode
For GCM mode ciphers, the behaviour of the EVP interface is subtly
altered and several additional ctrl operations are supported.
To specify any additional authenticated data (AAD), a call to
EVP_CipherUpdate(), EVP_EncryptUpdate(), or EVP_DecryptUpdate() should be
made with the output parameter out set to NULL.
When decrypting, the return value of EVP_DecryptFinal() or
EVP_CipherFinal() indicates if the operation was successful. If it does
not indicate success, the authentication operation has failed and any
output data MUST NOT be used as it is corrupted.
The following ctrls are supported in GCM mode:
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, ivlen, NULL)
Sets the IV length: this call can only be made before specifying
an IV. If not called, a default IV length is used. For GCM AES
the default is 12, i.e. 96 bits.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, taglen, tag)
Writes taglen bytes of the tag value to the buffer indicated by
tag. This call can only be made when encrypting data and after
all data has been processed, e.g. after an EVP_EncryptFinal()
call.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, taglen, tag)
Sets the expected tag to taglen bytes from tag. This call is
only legal when decrypting data and must be made before any data
is processed, e.g. before any EVP_DecryptUpdate call.
CCM mode
The behaviour of CCM mode ciphers is similar to GCM mode, but with a few
additional requirements and different ctrl values.
Like GCM mode any additional authenticated data (AAD) is passed by call-
ing EVP_CipherUpdate(), EVP_EncryptUpdate(), or EVP_DecryptUpdate() with
the output parameter out set to NULL. Additionally, the total plaintext
or ciphertext length MUST be passed to EVP_CipherUpdate(),
EVP_EncryptUpdate(), or EVP_DecryptUpdate() with the output and input
parameters (in and out) set to NULL and the length passed in the inl
parameter.
The following ctrls are supported in CCM mode:
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_TAG, taglen, tag)
This call is made to set the expected CCM tag value when decrypt-
ing or the length of the tag (with the tag parameter set to NULL)
when encrypting. The tag length is often referred to as M. If
not set, a default value is used (12 for AES).
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_L, ivlen, NULL)
Sets the CCM L value. If not set, a default is used (8 for AES).
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_CCM_SET_IVLEN, ivlen, NULL)
Sets the CCM nonce (IV) length: this call can only be made before
specifying a nonce value. The nonce length is given by 15 - L so
it is 7 by default for AES.
EXAMPLES
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};
const char intext[] = "Some Crypto Text";
EVP_CIPHER_CTX *ctx;
FILE *out;
ctx = EVP_CIPHER_CTX_new();
EVP_EncryptInit_ex(ctx, EVP_bf_cbc(), NULL, key, iv);
if (!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext,
strlen(intext))) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
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 */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
outlen += tmplen;
EVP_CIPHER_CTX_free(ctx);
/*
* Need binary mode for fopen because encrypted data is
* binary data. Also cannot use strlen() on it because
* it won't be NUL terminated and may contain embedded
* NULs.
*/
out = fopen(outfile, "wb");
if (out == NULL) {
/* Error */
return 0;
}
fwrite(outbuf, 1, outlen, out);
fclose(out);
return 1;
}
The ciphertext from the above example can be decrypted using the
openssl(1) utility with the command line:
openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F \
-iv 0102030405060708 -d
General encryption, decryption function example using FILE I/O and AES128
with an 128-bit key:
int
do_crypt(FILE *in, FILE *out, int do_encrypt)
{
/* Allow enough space in output buffer for additional block */
unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
int inlen, outlen;
EVP_CIPHER_CTX *ctx;
/*
* Bogus key and IV: we'd normally set these from
* another source.
*/
unsigned char key[] = "0123456789abcdeF";
unsigned char iv[] = "1234567887654321";
ctx = EVP_CIPHER_CTX_new();
EVP_CipherInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
do_encrypt);
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 */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
fwrite(outbuf, 1, outlen, out);
}
if (!EVP_CipherFinal_ex(ctx, outbuf, &outlen)) {
/* Error */
EVP_CIPHER_CTX_free(ctx);
return 0;
}
fwrite(outbuf, 1, outlen, out);
EVP_CIPHER_CTX_free(ctx);
return 1;
}
SEE ALSO
evp(3)
HISTORY
EVP_EncryptInit(), EVP_EncryptUpdate(), EVP_EncryptFinal(),
EVP_DecryptInit(), EVP_DecryptUpdate(), EVP_DecryptFinal(),
EVP_CipherInit(), EVP_CipherUpdate(), EVP_CipherFinal(),
EVP_get_cipherbyname(), EVP_des_cbc(), EVP_des_ecb(), EVP_des_cfb(),
EVP_des_ofb(), EVP_des_ede_cbc(), EVP_des_ede(), EVP_des_ede_ofb(),
EVP_des_ede_cfb(), EVP_des_ede3_cbc(), EVP_des_ede3(),
EVP_des_ede3_ofb(), EVP_des_ede3_cfb(), EVP_rc4(), EVP_idea_cbc(),
EVP_idea_ecb(), EVP_idea_cfb(), and EVP_idea_ofb() first appeared in
SSLeay 0.5.1. EVP_rc2_cbc(), EVP_rc2_ecb(), EVP_rc2_cfb(), and
EVP_rc2_ofb() first appeared in SSLeay 0.5.2. EVP_desx_cbc() first
appeared in SSLeay 0.6.2. EVP_CIPHER_block_size(),
EVP_CIPHER_key_length(), EVP_CIPHER_iv_length(), EVP_CIPHER_type(),
EVP_CIPHER_CTX_block_size(), EVP_CIPHER_CTX_key_length(),
EVP_CIPHER_CTX_iv_length(), and EVP_CIPHER_CTX_type() first appeared in
SSLeay 0.6.5. EVP_bf_cbc(), EVP_bf_ecb(), EVP_bf_cfb(), and EVP_bf_ofb()
first appeared in SSLeay 0.6.6. EVP_CIPHER_CTX_cleanup(),
EVP_get_cipherbyobj(), EVP_CIPHER_nid(), EVP_CIPHER_CTX_cipher(),
EVP_CIPHER_CTX_nid(), EVP_CIPHER_CTX_get_app_data(),
EVP_CIPHER_CTX_set_app_data(), and EVP_enc_null() first appeared in
SSLeay 0.8.0. EVP_get_cipherbynid() first appeared in SSLeay 0.8.1.
EVP_CIPHER_CTX_init(), EVP_CIPHER_param_to_asn1(), and
EVP_CIPHER_asn1_to_param() first appeared in SSLeay 0.9.0. All these
functions have been available since OpenBSD 2.4.
EVP_rc2_64_cbc() first appeared in SSL_eay 0.9.1. EVP_CIPHER_CTX_type()
first appeared in OpenSSL 0.9.3. These functions have been available
since OpenBSD 2.6.
EVP_CIPHER_CTX_set_key_length(), EVP_CIPHER_CTX_ctrl(),
EVP_CIPHER_flags(), EVP_CIPHER_mode(), EVP_CIPHER_CTX_flags(), and
EVP_CIPHER_CTX_mode() first appeared in OpenSSL 0.9.6 and have been
available since OpenBSD 2.9.
EVP_EncryptInit_ex(), EVP_EncryptFinal_ex(), EVP_DecryptInit_ex(),
EVP_DecryptFinal_ex(), EVP_CipherInit_ex(), EVP_CipherFinal_ex(), and
EVP_CIPHER_CTX_set_padding() first appeared in OpenSSL 0.9.7 and have
been available since OpenBSD 3.2.
EVP_CIPHER_CTX_rand_key() first appeared in OpenSSL 0.9.8.
EVP_CIPHER_CTX_new() and EVP_CIPHER_CTX_free() first appeared in OpenSSL
0.9.8b. These functions have been available since OpenBSD 4.5.
EVP_rc4_hmac_md5(), EVP_aes_128_gcm(), EVP_aes_192_gcm(),
EVP_aes_256_gcm(), EVP_aes_128_ccm(), EVP_aes_192_ccm(),
EVP_aes_256_ccm(), EVP_aes_128_cbc_hmac_sha1(), and
EVP_aes_256_cbc_hmac_sha1() first appeared in OpenSSL 1.0.1 and have been
available since OpenBSD 5.3.
EVP_CIPHER_CTX_reset() first appeared in OpenSSL 1.1.0 and has been
available since OpenBSD 6.3.
EVP_CIPHER_CTX_get_iv() and EVP_CIPHER_CTX_set_iv() first appeared in
LibreSSL 2.8.1 and has been available since OpenBSD 6.4.
BUGS
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 contain-
ing EVP_MAX_KEY_LENGTH bytes.
The ASN.1 code is incomplete (and sometimes inaccurate). It has only
been tested for certain common S/MIME ciphers (RC2, DES, triple DES) in
CBC mode.
DragonFly 5.5 September 12, 2018 DragonFly 5.5