c2e4f17c1a
libdes (which is still used out there) or other des implementations, the OpenSSL DES functions are renamed to begin with DES_ instead of des_. Compatibility routines are provided and declared by including openssl/des_old.h. Those declarations are the same as were in des.h when the OpenSSL project started, which is exactly how libdes looked at that time, and hopefully still looks today. The compatibility functions will be removed in some future release, at the latest in version 1.0.
379 lines
17 KiB
Text
379 lines
17 KiB
Text
=pod
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=head1 NAME
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DES_random_key, DES_set_key, DES_key_sched, DES_set_key_checked,
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DES_set_key_unchecked, DES_set_odd_parity, DES_is_weak_key,
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DES_ecb_encrypt, DES_ecb2_encrypt, DES_ecb3_encrypt, DES_ncbc_encrypt,
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DES_cfb_encrypt, DES_ofb_encrypt, DES_pcbc_encrypt, DES_cfb64_encrypt,
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DES_ofb64_encrypt, DES_xcbc_encrypt, DES_ede2_cbc_encrypt,
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DES_ede2_cfb64_encrypt, DES_ede2_ofb64_encrypt, DES_ede3_cbc_encrypt,
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DES_ede3_cbcm_encrypt, DES_ede3_cfb64_encrypt, DES_ede3_ofb64_encrypt,
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DES_read_password, DES_read_2passwords, DES_read_pw_string,
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DES_cbc_cksum, DES_quad_cksum, DES_string_to_key, DES_string_to_2keys,
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DES_fcrypt, DES_crypt, DES_enc_read, DES_enc_write - DES encryption
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=head1 SYNOPSIS
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#include <openssl/des.h>
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void DES_random_key(DES_cblock *ret);
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int DES_set_key(const_DES_cblock *key, DES_key_schedule *schedule);
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int DES_key_sched(const_DES_cblock *key, DES_key_schedule *schedule);
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int DES_set_key_checked(const_DES_cblock *key,
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DES_key_schedule *schedule);
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void DES_set_key_unchecked(const_DES_cblock *key,
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DES_key_schedule *schedule);
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void DES_set_odd_parity(DES_cblock *key);
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int DES_is_weak_key(const_DES_cblock *key);
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void DES_ecb_encrypt(const_DES_cblock *input, DES_cblock *output,
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DES_key_schedule *ks, int enc);
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void DES_ecb2_encrypt(const_DES_cblock *input, DES_cblock *output,
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DES_key_schedule *ks1, DES_key_schedule *ks2, int enc);
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void DES_ecb3_encrypt(const_DES_cblock *input, DES_cblock *output,
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DES_key_schedule *ks1, DES_key_schedule *ks2,
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DES_key_schedule *ks3, int enc);
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void DES_ncbc_encrypt(const unsigned char *input, unsigned char *output,
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long length, DES_key_schedule *schedule, DES_cblock *ivec,
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int enc);
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void DES_cfb_encrypt(const unsigned char *in, unsigned char *out,
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int numbits, long length, DES_key_schedule *schedule,
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DES_cblock *ivec, int enc);
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void DES_ofb_encrypt(const unsigned char *in, unsigned char *out,
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int numbits, long length, DES_key_schedule *schedule,
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DES_cblock *ivec);
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void DES_pcbc_encrypt(const unsigned char *input, unsigned char *output,
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long length, DES_key_schedule *schedule, DES_cblock *ivec,
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int enc);
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void DES_cfb64_encrypt(const unsigned char *in, unsigned char *out,
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long length, DES_key_schedule *schedule, DES_cblock *ivec,
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int *num, int enc);
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void DES_ofb64_encrypt(const unsigned char *in, unsigned char *out,
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long length, DES_key_schedule *schedule, DES_cblock *ivec,
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int *num);
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void DES_xcbc_encrypt(const unsigned char *input, unsigned char *output,
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long length, DES_key_schedule *schedule, DES_cblock *ivec,
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const_DES_cblock *inw, const_DES_cblock *outw, int enc);
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void DES_ede2_cbc_encrypt(const unsigned char *input,
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unsigned char *output, long length, DES_key_schedule *ks1,
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DES_key_schedule *ks2, DES_cblock *ivec, int enc);
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void DES_ede2_cfb64_encrypt(const unsigned char *in,
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unsigned char *out, long length, DES_key_schedule *ks1,
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DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc);
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void DES_ede2_ofb64_encrypt(const unsigned char *in,
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unsigned char *out, long length, DES_key_schedule *ks1,
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DES_key_schedule *ks2, DES_cblock *ivec, int *num);
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void DES_ede3_cbc_encrypt(const unsigned char *input,
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unsigned char *output, long length, DES_key_schedule *ks1,
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DES_key_schedule *ks2, DES_key_schedule *ks3, DES_cblock *ivec,
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int enc);
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void DES_ede3_cbcm_encrypt(const unsigned char *in, unsigned char *out,
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long length, DES_key_schedule *ks1, DES_key_schedule *ks2,
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DES_key_schedule *ks3, DES_cblock *ivec1, DES_cblock *ivec2,
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int enc);
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void DES_ede3_cfb64_encrypt(const unsigned char *in, unsigned char *out,
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long length, DES_key_schedule *ks1, DES_key_schedule *ks2,
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DES_key_schedule *ks3, DES_cblock *ivec, int *num, int enc);
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void DES_ede3_ofb64_encrypt(const unsigned char *in, unsigned char *out,
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long length, DES_key_schedule *ks1,
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DES_key_schedule *ks2, DES_key_schedule *ks3,
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DES_cblock *ivec, int *num);
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int DES_read_password(DES_cblock *key, const char *prompt, int verify);
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int DES_read_2passwords(DES_cblock *key1, DES_cblock *key2,
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const char *prompt, int verify);
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int DES_read_pw_string(char *buf, int length, const char *prompt,
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int verify);
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DES_LONG DES_cbc_cksum(const unsigned char *input, DES_cblock *output,
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long length, DES_key_schedule *schedule,
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const_DES_cblock *ivec);
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DES_LONG DES_quad_cksum(const unsigned char *input, DES_cblock output[],
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long length, int out_count, DES_cblock *seed);
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void DES_string_to_key(const char *str, DES_cblock *key);
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void DES_string_to_2keys(const char *str, DES_cblock *key1,
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DES_cblock *key2);
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char *DES_fcrypt(const char *buf, const char *salt, char *ret);
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char *DES_crypt(const char *buf, const char *salt);
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int DES_enc_read(int fd, void *buf, int len, DES_key_schedule *sched,
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DES_cblock *iv);
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int DES_enc_write(int fd, const void *buf, int len,
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DES_key_schedule *sched, DES_cblock *iv);
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=head1 DESCRIPTION
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This library contains a fast implementation of the DES encryption
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algorithm.
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There are two phases to the use of DES encryption. The first is the
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generation of a I<DES_key_schedule> from a key, the second is the
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actual encryption. A DES key is of type I<DES_cblock>. This type is
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consists of 8 bytes with odd parity. The least significant bit in
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each byte is the parity bit. The key schedule is an expanded form of
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the key; it is used to speed the encryption process.
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DES_random_key() generates a random key. The PRNG must be seeded
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prior to using this function (see L<rand(3)|rand(3)>; for backward
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compatibility the function DES_random_seed() is available as well).
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If the PRNG could not generate a secure key, 0 is returned. In
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earlier versions of the library, DES_random_key() did not generate
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secure keys.
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Before a DES key can be used, it must be converted into the
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architecture dependent I<DES_key_schedule> via the
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DES_set_key_checked() or DES_set_key_unchecked() function.
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DES_set_key_checked() will check that the key passed is of odd parity
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and is not a week or semi-weak key. If the parity is wrong, then -1
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is returned. If the key is a weak key, then -2 is returned. If an
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error is returned, the key schedule is not generated.
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DES_set_key() (called DES_key_sched() in the MIT library) works like
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DES_set_key_checked() if the I<DES_check_key> flag is non-zero,
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otherwise like DES_set_key_unchecked(). These functions are available
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for compatibility; it is recommended to use a function that does not
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depend on a global variable.
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DES_set_odd_parity() (called DES_fixup_key_parity() in the MIT
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library) sets the parity of the passed I<key> to odd.
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DES_is_weak_key() returns 1 is the passed key is a weak key, 0 if it
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is ok. The probability that a randomly generated key is weak is
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1/2^52, so it is not really worth checking for them.
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The following routines mostly operate on an input and output stream of
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I<DES_cblock>s.
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DES_ecb_encrypt() is the basic DES encryption routine that encrypts or
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decrypts a single 8-byte I<DES_cblock> in I<electronic code book>
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(ECB) mode. It always transforms the input data, pointed to by
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I<input>, into the output data, pointed to by the I<output> argument.
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If the I<encrypt> argument is non-zero (DES_ENCRYPT), the I<input>
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(cleartext) is encrypted in to the I<output> (ciphertext) using the
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key_schedule specified by the I<schedule> argument, previously set via
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I<DES_set_key>. If I<encrypt> is zero (DES_DECRYPT), the I<input> (now
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ciphertext) is decrypted into the I<output> (now cleartext). Input
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and output may overlap. DES_ecb_encrypt() does not return a value.
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DES_ecb3_encrypt() encrypts/decrypts the I<input> block by using
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three-key Triple-DES encryption in ECB mode. This involves encrypting
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the input with I<ks1>, decrypting with the key schedule I<ks2>, and
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then encrypting with I<ks3>. This routine greatly reduces the chances
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of brute force breaking of DES and has the advantage of if I<ks1>,
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I<ks2> and I<ks3> are the same, it is equivalent to just encryption
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using ECB mode and I<ks1> as the key.
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The macro DES_ecb2_encrypt() is provided to perform two-key Triple-DES
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encryption by using I<ks1> for the final encryption.
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DES_ncbc_encrypt() encrypts/decrypts using the I<cipher-block-chaining>
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(CBC) mode of DES. If the I<encrypt> argument is non-zero, the
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routine cipher-block-chain encrypts the cleartext data pointed to by
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the I<input> argument into the ciphertext pointed to by the I<output>
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argument, using the key schedule provided by the I<schedule> argument,
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and initialization vector provided by the I<ivec> argument. If the
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I<length> argument is not an integral multiple of eight bytes, the
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last block is copied to a temporary area and zero filled. The output
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is always an integral multiple of eight bytes.
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DES_xcbc_encrypt() is RSA's DESX mode of DES. It uses I<inw> and
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I<outw> to 'whiten' the encryption. I<inw> and I<outw> are secret
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(unlike the iv) and are as such, part of the key. So the key is sort
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of 24 bytes. This is much better than CBC DES.
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DES_ede3_cbc_encrypt() implements outer triple CBC DES encryption with
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three keys. This means that each DES operation inside the CBC mode is
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really an C<C=E(ks3,D(ks2,E(ks1,M)))>. This mode is used by SSL.
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The DES_ede2_cbc_encrypt() macro implements two-key Triple-DES by
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reusing I<ks1> for the final encryption. C<C=E(ks1,D(ks2,E(ks1,M)))>.
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This form of Triple-DES is used by the RSAREF library.
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DES_pcbc_encrypt() encrypt/decrypts using the propagating cipher block
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chaining mode used by Kerberos v4. Its parameters are the same as
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DES_ncbc_encrypt().
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DES_cfb_encrypt() encrypt/decrypts using cipher feedback mode. This
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method takes an array of characters as input and outputs and array of
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characters. It does not require any padding to 8 character groups.
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Note: the I<ivec> variable is changed and the new changed value needs to
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be passed to the next call to this function. Since this function runs
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a complete DES ECB encryption per I<numbits>, this function is only
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suggested for use when sending small numbers of characters.
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DES_cfb64_encrypt()
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implements CFB mode of DES with 64bit feedback. Why is this
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useful you ask? Because this routine will allow you to encrypt an
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arbitrary number of bytes, no 8 byte padding. Each call to this
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routine will encrypt the input bytes to output and then update ivec
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and num. num contains 'how far' we are though ivec. If this does
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not make much sense, read more about cfb mode of DES :-).
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DES_ede3_cfb64_encrypt() and DES_ede2_cfb64_encrypt() is the same as
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DES_cfb64_encrypt() except that Triple-DES is used.
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DES_ofb_encrypt() encrypts using output feedback mode. This method
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takes an array of characters as input and outputs and array of
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characters. It does not require any padding to 8 character groups.
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Note: the I<ivec> variable is changed and the new changed value needs to
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be passed to the next call to this function. Since this function runs
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a complete DES ECB encryption per numbits, this function is only
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suggested for use when sending small numbers of characters.
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DES_ofb64_encrypt() is the same as DES_cfb64_encrypt() using Output
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Feed Back mode.
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DES_ede3_ofb64_encrypt() and DES_ede2_ofb64_encrypt() is the same as
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DES_ofb64_encrypt(), using Triple-DES.
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The following functions are included in the DES library for
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compatibility with the MIT Kerberos library. DES_read_pw_string()
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is also available under the name EVP_read_pw_string().
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DES_read_pw_string() writes the string specified by I<prompt> to
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standard output, turns echo off and reads in input string from the
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terminal. The string is returned in I<buf>, which must have space for
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at least I<length> bytes. If I<verify> is set, the user is asked for
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the password twice and unless the two copies match, an error is
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returned. A return code of -1 indicates a system error, 1 failure due
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to use interaction, and 0 is success.
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DES_read_password() does the same and converts the password to a DES
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key by calling DES_string_to_key(); DES_read_2password() operates in
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the same way as DES_read_password() except that it generates two keys
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by using the DES_string_to_2key() function. DES_string_to_key() is
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available for backward compatibility with the MIT library. New
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applications should use a cryptographic hash function. The same
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applies for DES_string_to_2key().
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DES_cbc_cksum() produces an 8 byte checksum based on the input stream
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(via CBC encryption). The last 4 bytes of the checksum are returned
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and the complete 8 bytes are placed in I<output>. This function is
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used by Kerberos v4. Other applications should use
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L<EVP_DigestInit(3)|EVP_DigestInit(3)> etc. instead.
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DES_quad_cksum() is a Kerberos v4 function. It returns a 4 byte
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checksum from the input bytes. The algorithm can be iterated over the
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input, depending on I<out_count>, 1, 2, 3 or 4 times. If I<output> is
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non-NULL, the 8 bytes generated by each pass are written into
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I<output>.
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The following are DES-based transformations:
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DES_fcrypt() is a fast version of the Unix crypt(3) function. This
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version takes only a small amount of space relative to other fast
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crypt() implementations. This is different to the normal crypt in
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that the third parameter is the buffer that the return value is
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written into. It needs to be at least 14 bytes long. This function
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is thread safe, unlike the normal crypt.
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DES_crypt() is a faster replacement for the normal system crypt().
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This function calls DES_fcrypt() with a static array passed as the
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third parameter. This emulates the normal non-thread safe semantics
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of crypt(3).
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DES_enc_write() writes I<len> bytes to file descriptor I<fd> from
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buffer I<buf>. The data is encrypted via I<pcbc_encrypt> (default)
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using I<sched> for the key and I<iv> as a starting vector. The actual
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data send down I<fd> consists of 4 bytes (in network byte order)
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containing the length of the following encrypted data. The encrypted
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data then follows, padded with random data out to a multiple of 8
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bytes.
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DES_enc_read() is used to read I<len> bytes from file descriptor
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I<fd> into buffer I<buf>. The data being read from I<fd> is assumed to
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have come from DES_enc_write() and is decrypted using I<sched> for
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the key schedule and I<iv> for the initial vector.
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B<Warning:> The data format used by DES_enc_write() and DES_enc_read()
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has a cryptographic weakness: When asked to write more than MAXWRITE
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bytes, DES_enc_write() will split the data into several chunks that
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are all encrypted using the same IV. So don't use these functions
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unless you are sure you know what you do (in which case you might not
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want to use them anyway). They cannot handle non-blocking sockets.
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DES_enc_read() uses an internal state and thus cannot be used on
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multiple files.
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I<DES_rw_mode> is used to specify the encryption mode to use with
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DES_enc_read() and DES_end_write(). If set to I<DES_PCBC_MODE> (the
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default), DES_pcbc_encrypt is used. If set to I<DES_CBC_MODE>
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DES_cbc_encrypt is used.
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=head1 NOTES
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Single-key DES is insecure due to its short key size. ECB mode is
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not suitable for most applications; see L<DES_modes(7)|DES_modes(7)>.
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The L<evp(3)|evp(3)> library provides higher-level encryption functions.
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=head1 BUGS
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DES_3cbc_encrypt() is flawed and must not be used in applications.
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DES_cbc_encrypt() does not modify B<ivec>; use DES_ncbc_encrypt()
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instead.
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DES_cfb_encrypt() and DES_ofb_encrypt() operates on input of 8 bits.
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What this means is that if you set numbits to 12, and length to 2, the
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first 12 bits will come from the 1st input byte and the low half of
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the second input byte. The second 12 bits will have the low 8 bits
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taken from the 3rd input byte and the top 4 bits taken from the 4th
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input byte. The same holds for output. This function has been
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implemented this way because most people will be using a multiple of 8
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and because once you get into pulling bytes input bytes apart things
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get ugly!
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DES_read_pw_string() is the most machine/OS dependent function and
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normally generates the most problems when porting this code.
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=head1 CONFORMING TO
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ANSI X3.106
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The B<des> library was written to be source code compatible with
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the MIT Kerberos library.
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=head1 SEE ALSO
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crypt(3), L<des_modes(7)|des_modes(7)>, L<evp(3)|evp(3)>, L<rand(3)|rand(3)>
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=head1 HISTORY
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In OpenSSL 0.9.7, All des_ functions were renamed to DES_ to avoid
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clashes with older versions of libdes. Compatibility des_ functions
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are provided for a short while, as well as crypt().
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des_cbc_cksum(), des_cbc_encrypt(), des_ecb_encrypt(),
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des_is_weak_key(), des_key_sched(), des_pcbc_encrypt(),
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des_quad_cksum(), des_random_key(), des_read_password() and
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des_string_to_key() are available in the MIT Kerberos library;
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des_check_key_parity(), des_fixup_key_parity() and des_is_weak_key()
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are available in newer versions of that library.
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des_set_key_checked() and des_set_key_unchecked() were added in
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OpenSSL 0.9.5.
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des_generate_random_block(), des_init_random_number_generator(),
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des_new_random_key(), des_set_random_generator_seed() and
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des_set_sequence_number() and des_rand_data() are used in newer
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versions of Kerberos but are not implemented here.
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des_random_key() generated cryptographically weak random data in
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SSLeay and in OpenSSL prior version 0.9.5, as well as in the original
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MIT library.
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=head1 AUTHOR
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Eric Young (eay@cryptsoft.com). Modified for the OpenSSL project
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(http://www.openssl.org).
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=cut
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