path: root/src/lib/libcrypto/man/EVP_EncryptInit.3

.\" $OpenBSD: EVP_EncryptInit.3,v 1.48 2023/08/31 17:27:41 schwarze Exp $
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.\"   EVP_bf_cbc.pod EVP_cast5_cbc.pod EVP_idea_cbc.pod EVP_rc2_cbc.pod
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.Dd $Mdocdate: August 31 2023 $
.Dt EVP_ENCRYPTINIT 3
.Os
.Sh NAME
.Nm EVP_CIPHER_CTX_new ,
.Nm EVP_CIPHER_CTX_reset ,
.Nm EVP_CIPHER_CTX_cleanup ,
.Nm EVP_CIPHER_CTX_init ,
.Nm EVP_CIPHER_CTX_free ,
.Nm EVP_CIPHER_CTX_copy ,
.Nm EVP_EncryptInit_ex ,
.Nm EVP_EncryptUpdate ,
.Nm EVP_EncryptFinal_ex ,
.Nm EVP_DecryptInit_ex ,
.Nm EVP_DecryptUpdate ,
.Nm EVP_DecryptFinal_ex ,
.Nm EVP_CipherInit_ex ,
.Nm EVP_CipherUpdate ,
.Nm EVP_CipherFinal_ex ,
.Nm EVP_EncryptInit ,
.Nm EVP_EncryptFinal ,
.Nm EVP_DecryptInit ,
.Nm EVP_DecryptFinal ,
.Nm EVP_CipherInit ,
.Nm EVP_CipherFinal ,
.Nm EVP_Cipher ,
.Nm EVP_CIPHER_CTX_encrypting ,
.Nm EVP_get_cipherbyname ,
.Nm EVP_get_cipherbynid ,
.Nm EVP_get_cipherbyobj ,
.Nm EVP_CIPHER_CTX_cipher ,
.Nm EVP_enc_null ,
.Nm EVP_idea_cbc ,
.Nm EVP_idea_ecb ,
.Nm EVP_idea_cfb64 ,
.Nm EVP_idea_cfb ,
.Nm EVP_idea_ofb ,
.Nm EVP_rc2_cbc ,
.Nm EVP_rc2_ecb ,
.Nm EVP_rc2_cfb64 ,
.Nm EVP_rc2_cfb ,
.Nm EVP_rc2_ofb ,
.Nm EVP_rc2_40_cbc ,
.Nm EVP_rc2_64_cbc ,
.Nm EVP_bf_cbc ,
.Nm EVP_bf_ecb ,
.Nm EVP_bf_cfb64 ,
.Nm EVP_bf_cfb ,
.Nm EVP_bf_ofb ,
.Nm EVP_cast5_cbc ,
.Nm EVP_cast5_ecb ,
.Nm EVP_cast5_cfb64 ,
.Nm EVP_cast5_cfb ,
.Nm EVP_cast5_ofb
.Nd EVP cipher routines
.Sh SYNOPSIS
.In openssl/evp.h
.Ft EVP_CIPHER_CTX *
.Fn EVP_CIPHER_CTX_new void
.Ft int
.Fo EVP_CIPHER_CTX_reset
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_cleanup
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft void
.Fo EVP_CIPHER_CTX_init
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft void
.Fo EVP_CIPHER_CTX_free
.Fa "EVP_CIPHER_CTX *ctx"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_copy
.Fa "EVP_CIPHER_CTX *out"
.Fa "const EVP_CIPHER_CTX *in"
.Fc
.Ft int
.Fo EVP_EncryptInit_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "ENGINE *impl"
.Fa "const unsigned char *key"
.Fa "const unsigned char *iv"
.Fc
.Ft int
.Fo EVP_EncryptUpdate
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fa "const unsigned char *in"
.Fa "int inl"
.Fc
.Ft int
.Fo EVP_EncryptFinal_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_DecryptInit_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "ENGINE *impl"
.Fa "const unsigned char *key"
.Fa "const unsigned char *iv"
.Fc
.Ft int
.Fo EVP_DecryptUpdate
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fa "const unsigned char *in"
.Fa "int inl"
.Fc
.Ft int
.Fo EVP_DecryptFinal_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_CipherInit_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "ENGINE *impl"
.Fa "const unsigned char *key"
.Fa "const unsigned char *iv"
.Fa "int enc"
.Fc
.Ft int
.Fo EVP_CipherUpdate
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fa "const unsigned char *in"
.Fa "int inl"
.Fc
.Ft int
.Fo EVP_CipherFinal_ex
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_EncryptInit
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "const unsigned char *key"
.Fa "const unsigned char *iv"
.Fc
.Ft int
.Fo EVP_EncryptFinal
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_DecryptInit
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "const unsigned char *key"
.Fa "const unsigned char *iv"
.Fc
.Ft int
.Fo EVP_DecryptFinal
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_CipherInit
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "const EVP_CIPHER *type"
.Fa "const unsigned char *key"
.Fa "const unsigned char *iv"
.Fa "int enc"
.Fc
.Ft int
.Fo EVP_CipherFinal
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *outm"
.Fa "int *outl"
.Fc
.Ft int
.Fo EVP_Cipher
.Fa "EVP_CIPHER_CTX *ctx"
.Fa "unsigned char *out"
.Fa "const unsigned char *in"
.Fa "unsigned int inl"
.Fc
.Ft int
.Fo EVP_CIPHER_CTX_encrypting
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_get_cipherbyname
.Fa "const char *name"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_get_cipherbynid
.Fa "int nid"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_get_cipherbyobj
.Fa "const ASN1_OBJECT *a"
.Fc
.Ft const EVP_CIPHER *
.Fo EVP_CIPHER_CTX_cipher
.Fa "const EVP_CIPHER_CTX *ctx"
.Fc
.Sh DESCRIPTION
The EVP cipher routines are a high level interface to certain symmetric
ciphers.
.Pp
.Fn EVP_CIPHER_CTX_new
creates a new, empty cipher context.
.Pp
.Fn EVP_CIPHER_CTX_reset
clears all information from
.Fa ctx
and frees all allocated memory associated with it, except the
.Fa ctx
object itself, such that it can be reused for another series of calls to
.Fn EVP_CipherInit ,
.Fn EVP_CipherUpdate ,
and
.Fn EVP_CipherFinal .
.Fn EVP_CIPHER_CTX_cleanup
is a deprecated alias for
.Fn EVP_CIPHER_CTX_reset .
.Pp
.Fn 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
.Fn EVP_CIPHER_CTX_new
or one that was already used.
.Pp
.Fn EVP_CIPHER_CTX_free
clears all information from
.Fa ctx
and frees all allocated memory associated with it, including
.Fa ctx
itself.
This function should be called after all operations using a cipher
are complete, so sensitive information does not remain in memory.
If
.Fa ctx
is a
.Dv NULL
pointer, no action occurs.
.Pp
.Fn EVP_CIPHER_CTX_copy
calls
.Fn EVP_CIPHER_CTX_reset
on
.Fa out
and copies all the data from
.Fa in
to
.Fa out ,
except that the
.Vt EVP_CIPHER
and
.Vt ENGINE
objects used by
.Fa in
and any application specific data set with
.Xr EVP_CIPHER_CTX_set_app_data 3
are not copied and
.Fa out
will point to the same three objects.
The algorithm- and implementation-specific cipher data described in
.Xr EVP_CIPHER_CTX_get_cipher_data 3
is copied with
.Xr malloc 3
and
.Xr memcpy 3 ,
i.e. assuming that it does not contain pointers to any sub-objects.
If the bit
.Dv EVP_CIPH_CUSTOM_COPY
has been set with
.Xr EVP_CIPHER_meth_set_flags 3 ,
.Xr EVP_CIPHER_CTX_ctrl 3
is called at the end with arguments
.Fa in ,
.Dv EVP_CTRL_COPY ,
.No 0 ,
and
.Fa out
such that the cipher implementation can perform further algorithm-
and implementation-specific initializations after the algorithm-
and implementation-specific cipher data has been copied.
Among the cipher algorithms built into the library,
.Dv EVP_CIPH_CUSTOM_COPY
and
.Dv EVP_CTRL_COPY
are used by some of the ciphers documented in the
.Xr EVP_aes_256_gcm 3
manual page.
.Pp
.Fn EVP_EncryptInit_ex
sets up the cipher context
.Fa ctx
for encryption with cipher
.Fa type
from
.Vt ENGINE
.Fa impl .
.Fa type
is normally supplied by a function such as
.Xr EVP_aes_256_cbc 3 .
If
.Fa impl
is
.Dv NULL ,
then the default implementation is used.
.Fa key
is the symmetric key to use and
.Fa 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
.Dv NULL
except
.Fa type
in an initial call and supply the remaining parameters in subsequent
calls, all of which have
.Fa type
set to
.Dv NULL .
This is done when the default cipher parameters are not appropriate.
.Pp
.Fn EVP_EncryptUpdate
encrypts
.Fa inl
bytes from the buffer
.Fa in
and writes the encrypted version to
.Fa 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
.Fa out
should contain sufficient room.
The actual number of bytes written is placed in
.Fa outl .
.Pp
If padding is enabled (the default) then
.Fn 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
.Fa out
which should have sufficient space for one cipher block.
The number of bytes written is placed in
.Fa outl .
After this function is called, the encryption operation is finished and
no further calls to
.Fn EVP_EncryptUpdate
should be made.
.Pp
If padding is disabled then
.Fn 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.
.Pp
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptUpdate ,
and
.Fn EVP_DecryptFinal_ex
are the corresponding decryption operations.
.Fn 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
.Fa out
passed to
.Fn EVP_DecryptUpdate
should have sufficient room for (inl + cipher_block_size) bytes
unless the cipher block size is 1 in which case
.Fa inl
bytes is sufficient.
.Pp
.Fn EVP_CipherInit_ex ,
.Fn EVP_CipherUpdate ,
and
.Fn EVP_CipherFinal_ex
are functions that can be used for decryption or encryption.
The operation performed depends on the value of the
.Fa enc
parameter.
It should be set to 1 for encryption, 0 for decryption and -1 to leave
the value unchanged (the actual value of
.Fa enc
being supplied in a previous call).
.Pp
.Fn EVP_EncryptInit ,
.Fn EVP_DecryptInit ,
and
.Fn EVP_CipherInit
are deprecated functions behaving like
.Fn EVP_EncryptInit_ex ,
.Fn EVP_DecryptInit_ex ,
and
.Fn EVP_CipherInit_ex
except that they always use the default cipher implementation
and that they require
.Fn EVP_CIPHER_CTX_reset
before they can be used on a context that was already used.
.Pp
.Fn EVP_EncryptFinal ,
.Fn EVP_DecryptFinal ,
and
.Fn EVP_CipherFinal
are identical to
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptFinal_ex ,
and
.Fn EVP_CipherFinal_ex .
In previous releases of OpenSSL, they also used to clean up the
.Fa ctx ,
but this is no longer done and
.Fn EVP_CIPHER_CTX_reset
or
.Fn EVP_CIPHER_CTX_free
must be called to free any context resources.
.Pp
.Fn EVP_Cipher
encrypts or decrypts aligned blocks of data
whose lengths match the cipher block size.
It requires that the previous encryption or decryption operation
using the same
.Fa ctx ,
if there was any, ended exactly on a block boundary and that
.Fa inl
is an integer multiple of the cipher block size.
If either of these conditions is violated,
.Fn EVP_Cipher
silently produces incorrect results.
For that reason, using the function
.Fn EVP_CipherUpdate
instead is strongly recommended.
The latter can safely handle partial blocks, and even if
.Fa inl
actually is a multiple of the cipher block size for all calls,
the overhead incurred by using
.Fn EVP_CipherUpdate
is minimal.
.Pp
.Fn EVP_get_cipherbyname ,
.Fn EVP_get_cipherbynid ,
and
.Fn EVP_get_cipherbyobj
return an
.Vt EVP_CIPHER
structure when passed a cipher name, a NID or an
.Vt ASN1_OBJECT
structure.
.Pp
.Fn EVP_CIPHER_CTX_cipher
returns the
.Vt EVP_CIPHER
structure when passed an
.Vt EVP_CIPHER_CTX
structure.
.Pp
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.
.Pp
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.
.Pp
When decrypting, the final block is checked to see if it has the correct
form.
.Pp
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.
.Pp
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.
.Pp
The functions
.Fn EVP_EncryptInit ,
.Fn EVP_EncryptFinal ,
.Fn EVP_DecryptInit ,
.Fn EVP_CipherInit ,
and
.Fn EVP_CipherFinal
are obsolete but are retained for compatibility with existing code.
New code should use
.Fn EVP_EncryptInit_ex ,
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptFinal_ex ,
.Fn EVP_CipherInit_ex ,
and
.Fn EVP_CipherFinal_ex
because they can reuse an existing context without allocating and
freeing it up on each call.
.Pp
.Fn EVP_get_cipherbynid
and
.Fn EVP_get_cipherbyobj
are implemented as macros.
.Sh RETURN VALUES
.Fn EVP_CIPHER_CTX_new
returns a pointer to a newly created
.Vt EVP_CIPHER_CTX
for success or
.Dv NULL
for failure.
.Pp
.Fn EVP_CIPHER_CTX_reset ,
.Fn EVP_CIPHER_CTX_cleanup ,
.Fn EVP_CIPHER_CTX_copy ,
.Fn EVP_EncryptInit_ex ,
.Fn EVP_EncryptUpdate ,
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptUpdate ,
.Fn EVP_DecryptFinal_ex ,
.Fn EVP_CipherInit_ex ,
.Fn EVP_CipherUpdate ,
.Fn EVP_CipherFinal_ex ,
.Fn EVP_EncryptInit ,
.Fn EVP_EncryptFinal ,
.Fn EVP_DecryptInit ,
.Fn EVP_DecryptFinal ,
.Fn EVP_CipherInit ,
.Fn EVP_CipherFinal ,
and
.Fn EVP_Cipher
return 1 for success or 0 for failure.
.Pp
.Fn EVP_CIPHER_CTX_encrypting
returns 1 if
.Fa ctx
is initialized for encryption or 0 otherwise, in which case
it may be uninitialized or initialized for decryption.
.Pp
.Fn EVP_get_cipherbyname ,
.Fn EVP_get_cipherbynid ,
and
.Fn EVP_get_cipherbyobj
return an
.Vt EVP_CIPHER
structure or
.Dv NULL
on error.
.Pp
.Fn EVP_CIPHER_CTX_cipher
returns an
.Vt EVP_CIPHER
structure.
.Sh CIPHER LISTING
All algorithms have a fixed key length unless otherwise stated.
.Bl -tag -width Ds
.It Fn EVP_enc_null
Null cipher: does nothing.
.It Xo
.Fn EVP_idea_cbc ,
.Fn EVP_idea_ecb ,
.Fn EVP_idea_cfb64 ,
.Fn EVP_idea_ofb
.Xc
IDEA encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
.Fn EVP_idea_cfb
is an alias for
.Fn EVP_idea_cfb64 ,
implemented as a macro.
.It Xo
.Fn EVP_rc2_cbc ,
.Fn EVP_rc2_ecb ,
.Fn EVP_rc2_cfb64 ,
.Fn EVP_rc2_ofb
.Xc
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.
.Fn EVP_rc2_cfb
is an alias for
.Fn EVP_rc2_cfb64 ,
implemented as a macro.
.It Xo
.Fn EVP_rc2_40_cbc ,
.Fn EVP_rc2_64_cbc
.Xc
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
.Fn EVP_rc2_cbc ,
.Xr EVP_CIPHER_CTX_set_key_length 3 ,
and
.Xr EVP_CIPHER_CTX_ctrl 3
to set the key length and effective key length.
.It Xo
.Fn EVP_bf_cbc ,
.Fn EVP_bf_ecb ,
.Fn EVP_bf_cfb64 ,
.Fn EVP_bf_ofb
.Xc
Blowfish encryption algorithm in CBC, ECB, CFB and OFB modes
respectively.
This is a variable key length cipher.
.Fn EVP_bf_cfb
is an alias for
.Fn EVP_bf_cfb64 ,
implemented as a macro.
.It Xo
.Fn EVP_cast5_cbc ,
.Fn EVP_cast5_ecb ,
.Fn EVP_cast5_cfb64 ,
.Fn EVP_cast5_ofb
.Xc
CAST encryption algorithm in CBC, ECB, CFB and OFB modes respectively.
This is a variable key length cipher.
.Fn EVP_cast5_cfb
is an alias for
.Fn EVP_cast5_cfb64 ,
implemented as a macro.
.El
.Pp
See also
.Xr EVP_aes_128_cbc 3 ,
.Xr EVP_camellia_128_cbc 3 ,
.Xr EVP_des_cbc 3 ,
.Xr EVP_rc4 3 ,
and
.Xr EVP_sm4_cbc 3 .
.Ss GCM mode
For GCM mode ciphers, the behaviour of the EVP interface
is subtly altered and several additional ctrl operations are
supported.
.Pp
To specify any additional authenticated data (AAD), a call to
.Fn EVP_CipherUpdate ,
.Fn EVP_EncryptUpdate ,
or
.Fn EVP_DecryptUpdate
should be made with the output parameter out set to
.Dv NULL .
.Pp
When decrypting, the return value of
.Fn EVP_DecryptFinal
or
.Fn 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.
.Pp
The following ctrls are supported in GCM mode:
.Bl -tag -width Ds
.It Fn 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.
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_GET_TAG taglen tag
Writes
.Fa taglen
bytes of the tag value to the buffer indicated by
.Fa tag .
This call can only be made when encrypting data and after all data has
been processed, e.g. after an
.Fn EVP_EncryptFinal
call.
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_GCM_SET_TAG taglen tag
Sets the expected tag to
.Fa taglen
bytes from
.Fa tag .
This call is only legal when decrypting data and must be made before
any data is processed, e.g. before any
.Fa EVP_DecryptUpdate
call.
.El
.Ss CCM mode
The behaviour of CCM mode ciphers is similar to GCM mode, but with
a few additional requirements and different ctrl values.
.Pp
Like GCM mode any additional authenticated data (AAD) is passed
by calling
.Fn EVP_CipherUpdate ,
.Fn EVP_EncryptUpdate ,
or
.Fn EVP_DecryptUpdate
with the output parameter out set to
.Dv NULL .
Additionally, the total
plaintext or ciphertext length MUST be passed to
.Fn EVP_CipherUpdate ,
.Fn EVP_EncryptUpdate ,
or
.Fn EVP_DecryptUpdate
with the output and input
parameters
.Pq Fa in No and Fa out
set to
.Dv NULL
and the length passed in the
.Fa inl
parameter.
.Pp
The following ctrls are supported in CCM mode:
.Bl -tag -width Ds
.It Fn EVP_CIPHER_CTX_ctrl ctx EVP_CTRL_CCM_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
.Fa tag
parameter set to
.Dv NULL )
when encrypting.
The tag length is often referred to as M.
If not set, a default value is used (12 for AES).
.It Fn 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).
.It Fn 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.
.El
.Sh EXAMPLES
Encrypt a string using blowfish:
.Bd -literal -offset 3n
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;
}
.Ed
.Pp
The ciphertext from the above example can be decrypted using the
.Xr openssl 1
utility with the command line:
.Bd -literal -offset indent
openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F \e
           -iv 0102030405060708 -d
.Ed
.Pp
General encryption, decryption function example using FILE I/O and AES128
with a 128-bit key:
.Bd -literal
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;
}
.Ed
.Sh SEE ALSO
.Xr BIO_f_cipher 3 ,
.Xr evp 3 ,
.Xr EVP_AEAD_CTX_init 3 ,
.Xr EVP_aes_128_cbc 3 ,
.Xr EVP_camellia_128_cbc 3 ,
.Xr EVP_chacha20 3 ,
.Xr EVP_CIPHER_CTX_ctrl 3 ,
.Xr EVP_CIPHER_CTX_get_cipher_data 3 ,
.Xr EVP_CIPHER_CTX_set_flags 3 ,
.Xr EVP_CIPHER_nid 3 ,
.Xr EVP_des_cbc 3 ,
.Xr EVP_OpenInit 3 ,
.Xr EVP_rc4 3 ,
.Xr EVP_SealInit 3 ,
.Xr EVP_sm4_cbc 3
.Sh HISTORY
.Fn EVP_EncryptInit ,
.Fn EVP_EncryptUpdate ,
.Fn EVP_EncryptFinal ,
.Fn EVP_DecryptInit ,
.Fn EVP_DecryptUpdate ,
.Fn EVP_DecryptFinal ,
.Fn EVP_CipherInit ,
.Fn EVP_CipherUpdate ,
.Fn EVP_CipherFinal ,
.Fn EVP_get_cipherbyname ,
.Fn EVP_idea_cbc ,
.Fn EVP_idea_ecb ,
.Fn EVP_idea_cfb ,
and
.Fn EVP_idea_ofb
first appeared in SSLeay 0.5.1.
.Fn EVP_rc2_cbc ,
.Fn EVP_rc2_ecb ,
.Fn EVP_rc2_cfb ,
and
.Fn EVP_rc2_ofb
first appeared in SSLeay 0.5.2.
.Fn EVP_Cipher
first appeared in SSLeay 0.6.5.
.Fn EVP_bf_cbc ,
.Fn EVP_bf_ecb ,
.Fn EVP_bf_cfb ,
and
.Fn EVP_bf_ofb
first appeared in SSLeay 0.6.6.
.Fn EVP_CIPHER_CTX_cleanup ,
.Fn EVP_get_cipherbyobj ,
.Fn EVP_CIPHER_CTX_cipher ,
and
.Fn EVP_enc_null
first appeared in SSLeay 0.8.0.
.Fn EVP_get_cipherbynid
first appeared in SSLeay 0.8.1.
.Fn EVP_CIPHER_CTX_init
first appeared in SSLeay 0.9.0.
All these functions have been available since
.Ox 2.4 .
.Pp
.Fn EVP_rc2_40_cbc
and
.Fn EVP_rc2_64_cbc
first appeared in SSLeay 0.9.1 and have been available since
.Ox 2.6 .
.Pp
.Fn EVP_EncryptInit_ex ,
.Fn EVP_EncryptFinal_ex ,
.Fn EVP_DecryptInit_ex ,
.Fn EVP_DecryptFinal_ex ,
.Fn EVP_CipherInit_ex ,
and
.Fn EVP_CipherFinal_ex
first appeared in OpenSSL 0.9.7 and have been available since
.Ox 3.2 .
.Pp
.Fn EVP_bf_cfb64 ,
.Fn EVP_cast5_cfb64 ,
.Fn EVP_idea_cfb64 ,
and
.Fn EVP_rc2_cfb64
first appeared in OpenSSL 0.9.7e and have been available since
.Ox 3.8 .
.Pp
.Fn EVP_CIPHER_CTX_new
and
.Fn EVP_CIPHER_CTX_free
first appeared in OpenSSL 0.9.8b and have been available since
.Ox 4.5 .
.Pp
.Fn EVP_CIPHER_CTX_copy
first appeared in OpenSSL 1.0.0
and has been available since
.Ox 4.9 .
.Pp
.Fn EVP_CIPHER_CTX_reset
first appeared in OpenSSL 1.1.0 and has been available since
.Ox 6.3 .
.Pp
.Fn EVP_CIPHER_CTX_encrypting
first appeared in OpenSSL 1.1.0 and has been available since
.Ox 6.4 .
.Sh BUGS
.Fn EVP_CIPHER_CTX_copy
may already have cleared the data in
.Fa out
and copied some new data into it even if it fails and returns 0.