EVP_ENCRYPTINIT(3) OpenSSL EVP_ENCRYPTINIT(3)
NAME
EVP_CIPHER_CTX_new, EVP_CIPHER_CTX_reset, 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_CIPHER_CTX_set_key_length, EVP_CIPHER_CTX_ctrl, 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_enc_null - 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);
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);
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);
int 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 cipher context.
EVP_CIPHER_CTX_free() clears all information from a cipher context and
free up any allocated memory associate 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.
EVP_EncryptInit_ex() sets up cipher context ctx for encryption with
cipher type from ENGINE impl. ctx must be created 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
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. For most ciphers
and modes, the amount of data written can be anything from zero bytes
to (inl + cipher_block_size - 1) bytes. For wrap cipher modes, the
amount of data written can be anything from zero bytes to (inl +
cipher_block_size) bytes. For stream ciphers, the amount of data
written can be anything from zero bytes to inl bytes. Thus, out should
contain sufficient room for the operation being performed. The actual
number of bytes written is placed in outl. It also checks if in and out
are partially overlapping, and if they are 0 is returned to indicate
failure.
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 standard block padding (aka PKCS padding) as described in the
NOTES section, below. 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 encryption operations except that if padding is enabled 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.
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_CIPHER_CTX_reset() clears all information from a cipher context and
free up any allocated memory associate with it, except the ctx itself.
This function should be called anytime ctx is to be reused for another
EVP_CipherInit() / EVP_CipherUpdate() / EVP_CipherFinal() series of
calls.
EVP_EncryptInit(), EVP_DecryptInit() and EVP_CipherInit() behave in a
similar way to EVP_EncryptInit_ex(), EVP_DecryptInit_ex() and
EVP_CipherInit_ex() except they always use the default cipher
implementation.
EVP_EncryptFinal(), EVP_DecryptFinal() and EVP_CipherFinal() are
identical to EVP_EncryptFinal_ex(), EVP_DecryptFinal_ex() and
EVP_CipherFinal_ex(). In previous releases they also cleaned up the
ctx, but this is no longer done and EVP_CIPHER_CTX_clean() 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
IDENTIFIER.
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 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_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 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,
EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE,
EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE, EVP_CIPH_WRAP_MODE or
EVP_CIPH_OCB_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.
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. Key
must point to a buffer at least as big as the value returned by
EVP_CIPHER_CTX_key_length().
RETURN VALUES
EVP_CIPHER_CTX_new() returns a pointer to a newly created
EVP_CIPHER_CTX for success and NULL for failure.
EVP_EncryptInit_ex(), EVP_EncryptUpdate() 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_reset() 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
greater than zero for success and zero or a negative number on failure.
EVP_CIPHER_CTX_rand_key() returns 1 for success.
CIPHER LISTING
All algorithms have a fixed key length unless otherwise stated.
Refer to "SEE ALSO" for the full list of ciphers available through the
EVP interface.
EVP_enc_null()
Null cipher: does nothing.
AEAD Interface
The EVP interface for Authenticated Encryption with Associated Data
(AEAD) modes are subtly altered and several additional ctrl operations
are supported depending on the mode specified.
To specify 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 whether 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.
GCM and OCB Modes
The following ctrls are supported in GCM and OCB modes.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_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 and OCB AES the default is 12 (i.e. 96 bits). For OCB
mode the maximum is 15.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_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).
For OCB, "taglen" must either be 16 or the value previously set via
EVP_CTRL_AEAD_SET_TAG.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
Sets the expected tag to "taglen" bytes from "tag". The tag length
can only be set before specifying an IV. "taglen" must be between
1 and 16 inclusive.
For GCM, this call is only valid when decrypting data.
For OCB, this call is valid when decrypting data to set the
expected tag, and before encryption to set the desired tag length.
In OCB mode, calling this before encryption with "tag" set to
"NULL" sets the tag length. If this is not called prior to
encryption, a default tag length is used.
For OCB AES, the default tag length is 16 (i.e. 128 bits). It is
also the maximum tag length for OCB.
CCM Mode
The EVP interface for CCM mode is similar to that of the GCM mode but
with a few additional requirements and different ctrl values.
For CCM mode, 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_AEAD_SET_TAG, taglen, tag)
This call is made to set the expected CCM tag value when decrypting
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). When decrypting, the tag
needs to be set before passing in data to be decrypted, but as in
GCM and OCB mode, it can be set after passing additional
authenticated data (see "AEAD Interface").
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_AEAD_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.
ChaCha20-Poly1305
The following ctrls are supported for the ChaCha20-Poly1305 AEAD
algorithm.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
Sets the nonce length. This call can only be made before specifying
the nonce. If not called a default nonce length of 12 (i.e. 96
bits) is used. The maximum nonce length is 12 bytes (i.e. 96-bits).
If a nonce of less than 12 bytes is set then the nonce is
automatically padded with leading 0 bytes to make it 12 bytes in
length.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_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).
"taglen" specified here must be 16 (POLY1305_BLOCK_SIZE, i.e.
128-bits) or less.
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, taglen, tag)
Sets the expected tag to "taglen" bytes from "tag". The tag length
can only be set before specifying an IV. "taglen" must be between
1 and 16 (POLY1305_BLOCK_SIZE) inclusive. This call is only valid
when decrypting data.
NOTES
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.
Additionally, the EVP interface will ensure the use of platform
specific cryptographic acceleration such as AES-NI (the low-level
interfaces do not provide the guarantee).
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.
There are some differences between functions EVP_CipherInit() and
EVP_CipherInit_ex(), significant in some circumstances.
EVP_CipherInit() fills the passed context object with zeros. As a
consequence, EVP_CipherInit() does not allow step-by-step
initialization of the ctx when the key and iv are passed in separate
calls. It also means that the flags set for the CTX are removed, and it
is especially important for the EVP_CIPHER_CTX_FLAG_WRAP_ALLOW flag
treated specially in EVP_CipherInit_ex().
EVP_get_cipherbynid(), and EVP_get_cipherbyobj() are implemented as
macros.
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
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.
EXAMPLES
Encrypt a string using IDEA:
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;
ctx = EVP_CIPHER_CTX_new();
EVP_EncryptInit_ex(ctx, EVP_idea_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 utility with the command line (shown on two lines for clarity):
openssl idea -d \
-K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 <filename
General encryption and decryption function example using FILE I/O and
AES128 with a 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";
/* Don't set key or IV right away; we want to check lengths */
ctx = EVP_CIPHER_CTX_new();
EVP_CipherInit_ex(ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
do_encrypt);
OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
/* 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 */
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(7)
Supported ciphers are listed in:
EVP_aes(3), EVP_aria(3), EVP_bf(3), EVP_camellia(3), EVP_cast5(3),
EVP_chacha20(3), EVP_des(3), EVP_desx(3), EVP_idea(3), EVP_rc2(3),
EVP_rc4(3), EVP_rc5(3), EVP_seed(3), EVP_sm4(3)
HISTORY
Support for OCB mode was added in OpenSSL 1.1.0.
EVP_CIPHER_CTX was made opaque in OpenSSL 1.1.0. As a result,
EVP_CIPHER_CTX_reset() appeared and EVP_CIPHER_CTX_cleanup()
disappeared. EVP_CIPHER_CTX_init() remains as an alias for
EVP_CIPHER_CTX_reset().
COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>;.
1.1.1k 2021-03-25 EVP_ENCRYPTINIT(3)
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