.\" $OpenBSD: DES_set_key.3,v 1.16 2023/11/16 20:27:43 schwarze Exp $
.\" full merge up to:
.\" OpenSSL man3/DES_random_key 521738e9 Oct 5 14:58:30 2018 -0400
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.Dd $Mdocdate: November 16 2023 $
.Dt DES_SET_KEY 3
.Os
.Sh NAME
.Nm DES_random_key ,
.Nm DES_set_key ,
.Nm DES_key_sched ,
.Nm DES_set_key_checked ,
.Nm DES_set_key_unchecked ,
.Nm DES_set_odd_parity ,
.Nm DES_is_weak_key ,
.Nm DES_ecb_encrypt ,
.Nm DES_ecb2_encrypt ,
.Nm DES_ecb3_encrypt ,
.Nm DES_ncbc_encrypt ,
.Nm DES_cfb_encrypt ,
.Nm DES_ofb_encrypt ,
.Nm DES_pcbc_encrypt ,
.Nm DES_cfb64_encrypt ,
.Nm DES_ofb64_encrypt ,
.Nm DES_xcbc_encrypt ,
.Nm DES_ede2_cbc_encrypt ,
.Nm DES_ede2_cfb64_encrypt ,
.Nm DES_ede2_ofb64_encrypt ,
.Nm DES_ede3_cbc_encrypt ,
.Nm DES_ede3_cbcm_encrypt ,
.Nm DES_ede3_cfb64_encrypt ,
.Nm DES_ede3_ofb64_encrypt ,
.Nm DES_cbc_cksum ,
.Nm DES_quad_cksum ,
.Nm DES_string_to_key ,
.Nm DES_string_to_2keys ,
.Nm DES_fcrypt ,
.Nm DES_crypt ,
.Nm DES_enc_read ,
.Nm DES_enc_write
.Nd DES encryption
.Sh SYNOPSIS
.In openssl/des.h
.Ft void
.Fo DES_random_key
.Fa "DES_cblock *ret"
.Fc
.Ft int
.Fo DES_set_key
.Fa "const_DES_cblock *key"
.Fa "DES_key_schedule *schedule"
.Fc
.Ft int
.Fo DES_key_sched
.Fa "const_DES_cblock *key"
.Fa "DES_key_schedule *schedule"
.Fc
.Ft int
.Fo DES_set_key_checked
.Fa "const_DES_cblock *key"
.Fa "DES_key_schedule *schedule"
.Fc
.Ft void
.Fo DES_set_key_unchecked
.Fa "const_DES_cblock *key"
.Fa "DES_key_schedule *schedule"
.Fc
.Ft void
.Fo DES_set_odd_parity
.Fa "DES_cblock *key"
.Fc
.Ft int
.Fo DES_is_weak_key
.Fa "const_DES_cblock *key"
.Fc
.Ft void
.Fo DES_ecb_encrypt
.Fa "const_DES_cblock *input"
.Fa "DES_cblock *output"
.Fa "DES_key_schedule *ks"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ecb2_encrypt
.Fa "const_DES_cblock *input"
.Fa "DES_cblock *output"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ecb3_encrypt
.Fa "const_DES_cblock *input"
.Fa "DES_cblock *output"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_key_schedule *ks3"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ncbc_encrypt
.Fa "const unsigned char *input"
.Fa "unsigned char *output"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_cfb_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "int numbits"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ofb_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "int numbits"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fc
.Ft void
.Fo DES_pcbc_encrypt
.Fa "const unsigned char *input"
.Fa "unsigned char *output"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_cfb64_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fa "int *num"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ofb64_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fa "int *num"
.Fc
.Ft void
.Fo DES_xcbc_encrypt
.Fa "const unsigned char *input"
.Fa "unsigned char *output"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "DES_cblock *ivec"
.Fa "const_DES_cblock *inw"
.Fa "const_DES_cblock *outw"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ede2_cbc_encrypt
.Fa "const unsigned char *input"
.Fa "unsigned char *output"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_cblock *ivec"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ede2_cfb64_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_cblock *ivec"
.Fa "int *num"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ede2_ofb64_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_cblock *ivec"
.Fa "int *num"
.Fc
.Ft void
.Fo DES_ede3_cbc_encrypt
.Fa "const unsigned char *input"
.Fa "unsigned char *output"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_key_schedule *ks3"
.Fa "DES_cblock *ivec"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ede3_cbcm_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_key_schedule *ks3"
.Fa "DES_cblock *ivec1"
.Fa "DES_cblock *ivec2"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ede3_cfb64_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_key_schedule *ks3"
.Fa "DES_cblock *ivec"
.Fa "int *num"
.Fa "int enc"
.Fc
.Ft void
.Fo DES_ede3_ofb64_encrypt
.Fa "const unsigned char *in"
.Fa "unsigned char *out"
.Fa "long length"
.Fa "DES_key_schedule *ks1"
.Fa "DES_key_schedule *ks2"
.Fa "DES_key_schedule *ks3"
.Fa "DES_cblock *ivec"
.Fa "int *num"
.Fc
.Ft DES_LONG
.Fo DES_cbc_cksum
.Fa "const unsigned char *input"
.Fa "DES_cblock *output"
.Fa "long length"
.Fa "DES_key_schedule *schedule"
.Fa "const_DES_cblock *ivec"
.Fc
.Ft DES_LONG
.Fo DES_quad_cksum
.Fa "const unsigned char *input"
.Fa "DES_cblock output[]"
.Fa "long length"
.Fa "int out_count"
.Fa "DES_cblock *seed"
.Fc
.Ft void
.Fo DES_string_to_key
.Fa "const char *str"
.Fa "DES_cblock *key"
.Fc
.Ft void
.Fo DES_string_to_2keys
.Fa "const char *str"
.Fa "DES_cblock *key1"
.Fa "DES_cblock *key2"
.Fc
.Ft char *
.Fo DES_fcrypt
.Fa "const char *buf"
.Fa "const char *salt"
.Fa "char *ret"
.Fc
.Ft char *
.Fo DES_crypt
.Fa "const char *buf"
.Fa "const char *salt"
.Fc
.Ft int
.Fo DES_enc_read
.Fa "int fd"
.Fa "void *buf"
.Fa "int len"
.Fa "DES_key_schedule *sched"
.Fa "DES_cblock *iv"
.Fc
.Ft int
.Fo DES_enc_write
.Fa "int fd"
.Fa "const void *buf"
.Fa "int len"
.Fa "DES_key_schedule *sched"
.Fa "DES_cblock *iv"
.Fc
.Sh DESCRIPTION
This library contains a fast implementation of the DES encryption
algorithm.
.Pp
There are two phases to the use of DES encryption.
The first is the generation of a
.Vt DES_key_schedule
from a key, and the second is the actual encryption.
A DES key is of type
.Vt DES_cblock .
This type consists of 8 bytes with odd parity.
The least significant bit in each byte is the parity bit.
The key schedule is an expanded form of the key; it is used to speed the
encryption process.
.Pp
.Fn DES_random_key
generates a random key in odd parity.
.Pp
Before a DES key can be used, it must be converted into the architecture
dependent
.Vt DES_key_schedule
via the
.Fn DES_set_key_checked
or
.Fn DES_set_key_unchecked
function.
.Pp
.Fn DES_set_key_checked
will check that the key passed is of odd parity and is not a weak or
semi-weak key.
If the parity is wrong, then -1 is returned.
If the key is a weak key, then -2 is returned.
If an error is returned, the key schedule is not generated.
.Pp
.Fn DES_set_key
works like
.Fn DES_set_key_checked
if the
.Em DES_check_key
flag is non-zero, otherwise like
.Fn DES_set_key_unchecked .
These functions are available for compatibility; it is recommended to
use a function that does not depend on a global variable.
.Pp
.Fn DES_set_odd_parity
sets the parity of the passed
.Fa key
to odd.
.Pp
The following routines mostly operate on an input and output stream of
.Vt DES_cblock Ns s .
.Pp
.Fn DES_ecb_encrypt
is the basic DES encryption routine that encrypts or decrypts a single
8-byte
.Vt DES_cblock
in electronic code book (ECB) mode.
It always transforms the input data, pointed to by
.Fa input ,
into the output data, pointed to by the
.Fa output
argument.
If the
.Fa enc
argument is non-zero
.Pq Dv DES_ENCRYPT ,
the
.Fa input
(cleartext) is encrypted into the
.Fa output
(ciphertext) using the key_schedule specified by the
.Fa schedule
argument, previously set via
.Fn DES_set_key .
If
.Fa enc
is zero
.Pq Dv DES_DECRYPT ,
the
.Fa input
(now ciphertext) is decrypted into the
.Fa output
(now cleartext).
Input and output may overlap.
.Fn DES_ecb_encrypt
does not return a value.
.Pp
.Fn DES_ecb3_encrypt
encrypts/decrypts the
.Fa input
block by using three-key Triple-DES encryption in ECB mode.
This involves encrypting the input with
.Fa ks1 ,
decrypting with the key schedule
.Fa ks2 ,
and then encrypting with
.Fa ks3 .
This routine greatly reduces the chances of brute force breaking of DES
and has the advantage of if
.Fa ks1 ,
.Fa ks2 ,
and
.Fa ks3
are the same, it is equivalent to just encryption using ECB mode and
.Fa ks1
as the key.
.Pp
The macro
.Fn DES_ecb2_encrypt
is provided to perform two-key Triple-DES encryption by using
.Fa ks1
for the final encryption.
.Pp
.Fn DES_ncbc_encrypt
encrypts/decrypts using the cipher-block-chaining (CBC) mode of DES.
If the
.Fa enc
argument is non-zero, the routine cipher-block-chain encrypts the
cleartext data pointed to by the
.Fa input
argument into the ciphertext pointed to by the
.Fa output
argument, using the key schedule provided by the
.Fa schedule
argument, and initialization vector provided by the
.Fa ivec
argument.
If the
.Fa length
argument is not an integral multiple of eight bytes, the last block is
copied to a temporary area and zero filled.
The output is always an integral multiple of eight bytes.
.Pp
.Fn DES_xcbc_encrypt
is RSA's DESX mode of DES.
It uses
.Fa inw
and
.Fa outw
to "whiten" the encryption.
.Fa inw
and
.Fa outw
are secret (unlike the iv) and are as such, part of the key.
So the key is sort of 24 bytes.
This is much better than CBC DES.
.Pp
.Fn DES_ede3_cbc_encrypt
implements outer triple CBC DES encryption with three keys.
This means that each DES operation inside the CBC mode is
.Qq Li C=E(ks3,D(ks2,E(ks1,M))) .
This mode is used by SSL.
.Pp
The
.Fn DES_ede2_cbc_encrypt
macro implements two-key Triple-DES by reusing
.Fa ks1
for the final encryption.
.Qq Li C=E(ks1,D(ks2,E(ks1,M))) .
This form of Triple-DES is used by the RSAREF library.
.Pp
.Fn DES_pcbc_encrypt
encrypts/decrypts using the propagating cipher block chaining mode used
by Kerberos v4.
Its parameters are the same as
.Fn DES_ncbc_encrypt .
.Pp
.Fn DES_cfb_encrypt
encrypts/decrypts using cipher feedback mode.
This method takes an array of characters as input and outputs an array
of characters.
It does not require any padding to 8 character groups.
Note: the
.Fa ivec
variable is changed and the new changed value needs to be passed to the
next call to this function.
Since this function runs a complete DES ECB encryption per
.Fa numbits ,
this function is only suggested for use when sending a small number of
characters.
.Pp
.Fn DES_cfb64_encrypt
implements CFB mode of DES with 64-bit feedback.
Why is this useful you ask?
Because this routine will allow you to encrypt an arbitrary number of
bytes, without 8 byte padding.
Each call to this routine will encrypt the input bytes to output and
then update ivec and num.
num contains "how far" we are though ivec.
If this does not make much sense, read more about CFB mode of DES.
.Pp
The
.Fn DES_ede3_cfb64_encrypt
function and the
.Fn DES_ede2_cfb64_encrypt
macro are the same as
.Fn DES_cfb64_encrypt
except that Triple-DES is used.
.Pp
.Fn DES_ofb_encrypt
encrypts using output feedback mode.
This method takes an array of characters as input and outputs an array
of characters.
It does not require any padding to 8 character groups.
Note: the
.Fa ivec
variable is changed and the new changed value needs to be passed to the
next call to this function.
Since this function runs a complete DES ECB encryption per
.Fa numbits ,
this function is only suggested for use when sending a small number
of characters.
.Pp
.Fn DES_ofb64_encrypt
is the same as
.Fn DES_cfb64_encrypt
using Output Feed Back mode.
.Pp
The
.Fn DES_ede3_ofb64_encrypt
function and the
.Fn DES_ede2_ofb64_encrypt
macro are the same as
.Fn DES_ofb64_encrypt ,
using Triple-DES.
.Pp
The following functions are included in the DES library for
compatibility with the MIT Kerberos library.
.Pp
.Fn DES_cbc_cksum
produces an 8-byte checksum based on the input stream (via CBC
encryption).
The last 4 bytes of the checksum are returned and the complete 8 bytes
are placed in
.Fa output .
This function is used by Kerberos v4.
Other applications should use
.Xr EVP_DigestInit 3
etc. instead.
.Pp
.Fn DES_quad_cksum
is a Kerberos v4 function.
It returns a 4-byte checksum from the input bytes.
The algorithm can be iterated over the input, depending on
.Fa out_count ,
1, 2, 3 or 4 times.
If
.Fa output
is
.Pf non- Dv NULL ,
the 8 bytes generated by each pass are written into
.Fa output .
.Pp
The following are DES-based transformations:
.Pp
.Fn DES_fcrypt
is a fast version of the Unix
.Xr crypt 3
function.
The
.Fa salt
must be two ASCII characters.
This version is different from the normal crypt in that the third
parameter is the buffer that the return value is written into.
It needs to be at least 14 bytes long.
The fourteenth byte is set to NUL.
This version takes only a small amount of space relative to other
fast crypt implementations.
It is thread safe, unlike the normal crypt.
.Pp
.Fn DES_crypt
is a faster replacement for the normal system
.Xr crypt 3 .
This function calls
.Fn DES_fcrypt
with a static array passed as the third parameter.
This emulates the normal non-thread safe semantics of
.Xr crypt 3 .
.Pp
.Fn DES_enc_write
writes
.Fa len
bytes to file descriptor
.Fa fd
from buffer
.Fa buf .
The data is encrypted via
.Em pcbc_encrypt
(default) using
.Fa sched
for the key and
.Fa iv
as a starting vector.
The actual data send down
.Fa fd
consists of 4 bytes (in network byte order) containing the length of the
following encrypted data.
The encrypted data then follows, padded with random data out to a
multiple of 8 bytes.
.Pp
.Fn DES_enc_read
is used to read
.Fa len
bytes from file descriptor
.Fa fd
into buffer
.Fa buf .
The data being read from
.Fa fd
is assumed to have come from
.Fn DES_enc_write
and is decrypted using
.Fa sched
for the key schedule and
.Fa iv
for the initial vector.
.Pp
.Sy Warning :
The data format used by
.Fn DES_enc_write
and
.Fn DES_enc_read
has a cryptographic weakness: when asked to write more than
.Dv MAXWRITE
bytes,
.Fn DES_enc_write
will split the data into several chunks that are all encrypted using the
same IV.
So don't use these functions unless you are sure you know what
you do (in which case you might not want to use them anyway).
They cannot handle non-blocking sockets.
.Fn DES_enc_read
uses an internal state and thus cannot be used on multiple files.
.Pp
.Em DES_rw_mode
is used to specify the encryption mode to use with
.Fn DES_enc_read .
If set to
.Dv DES_PCBC_MODE
(the default), DES_pcbc_encrypt is used.
If set to
.Dv DES_CBC_MODE ,
DES_cbc_encrypt is used.
.Sh RETURN VALUES
.Fn DES_set_key ,
.Fn DES_key_sched ,
and
.Fn DES_set_key_checked
return 0 on success or a negative value on error.
.Pp
.Fn DES_is_weak_key
returns 1 if the passed key is a weak key or 0 if it is ok.
.Pp
.Fn DES_cbc_cksum
and
.Fn DES_quad_cksum
return a 4-byte integer representing the last 4 bytes of the checksum
of the input.
.Pp
.Fn DES_fcrypt
returns a pointer to the caller-provided buffer
.Fa ret ,
and
.Fn DES_crypt
returns a pointer to a static buffer.
Both are allowed to return
.Dv NULL
to indicate failure, but currently, they cannot fail.
.Sh SEE ALSO
.Xr crypt 3 ,
.Xr EVP_des_cbc 3 ,
.Xr EVP_EncryptInit 3
.Sh STANDARDS
ANSI X3.106
.Pp
The DES library was initially written to be source code compatible
with the MIT Kerberos library.
.Sh HISTORY
.Fn DES_random_key ,
.Fn DES_set_key ,
.Fn DES_key_sched ,
.Fn DES_set_odd_parity ,
.Fn DES_is_weak_key ,
.Fn DES_ecb_encrypt ,
.Fn DES_cfb_encrypt ,
.Fn DES_ofb_encrypt ,
.Fn DES_pcbc_encrypt ,
.Fn DES_cfb64_encrypt ,
.Fn DES_ofb64_encrypt ,
.Fn DES_ede3_cbc_encrypt ,
.Fn DES_cbc_cksum ,
.Fn DES_quad_cksum ,
.Fn DES_string_to_key ,
.Fn DES_string_to_2keys ,
.Fn DES_crypt ,
.Fn DES_enc_read ,
and
.Fn DES_enc_write
appeared in SSLeay 0.4 or earlier.
.Fn DES_ncbc_encrypt
first appeared in SSLeay 0.4.2.
.Fn DES_ede2_cbc_encrypt
first appeared in SSLeay 0.4.4.
.Fn DES_ecb2_encrypt ,
.Fn DES_ecb3_encrypt ,
.Fn DES_ede2_cfb64_encrypt ,
.Fn DES_ede2_ofb64_encrypt ,
.Fn DES_ede3_cfb64_encrypt ,
and
.Fn DES_ede3_ofb64_encrypt
first appeared in SSLeay 0.5.1.
.Fn DES_xcbc_encrypt
first appeared in SSLeay 0.6.2.
.Fn DES_fcrypt
first appeared in SSLeay 0.6.5.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn DES_set_key_checked
and
.Fn DES_set_key_unchecked
first appeared in OpenSSL 0.9.5 and have been available since
.Ox 2.7 .
.Pp
In OpenSSL 0.9.7 and
.Ox 3.2 ,
all
.Sy des_
functions were renamed to
.Sy DES_
to avoid clashes with older versions of libdes.
.Sh AUTHORS
.An Eric Young Aq Mt eay@cryptsoft.com
.Sh CAVEATS
Single-key DES is insecure due to its short key size.
ECB mode is not suitable for most applications.
.Sh BUGS
DES_cbc_encrypt does not modify
.Fa ivec ;
use
.Fn DES_ncbc_encrypt
instead.
.Pp
.Fn DES_cfb_encrypt
and
.Fn DES_ofb_encrypt
operates on input of 8 bits.
What this means is that if you set numbits to 12, and length to 2, the
first 12 bits will come from the 1st input byte and the low half of the
second input byte.
The second 12 bits will have the low 8 bits taken from the 3rd input
byte and the top 4 bits taken from the 4th input byte.
The same holds for output.
This function has been implemented this way because most people will be
using a multiple of 8 and because once you get into pulling input
bytes apart things get ugly!
.Pp
.Fn DES_string_to_key
is available for backward compatibility with the MIT library.
New applications should use a cryptographic hash function.
The same applies for
.Fn DES_string_to_2key .