296 lines
13 KiB
Text
296 lines
13 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_cfb64_encrypt, DES_ede3_ofb64_encrypt,
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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 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_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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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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=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)>). If the PRNG
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could not generate a secure key, 0 is returned.
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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() 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() sets the parity of the passed I<key> to odd.
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DES_is_weak_key() returns 1 if the passed key is a weak key, 0 if it
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is ok.
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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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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.
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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)> 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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=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_string_to_key() is available for backward compatibility with the
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MIT library. New applications should use a cryptographic hash function.
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The same applies for DES_string_to_2key().
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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 NOTES
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Applications should use the higher level functions
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L<EVP_EncryptInit(3)> etc. instead of calling these
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functions directly.
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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)>.
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=head1 SEE ALSO
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L<des_modes(7)>,
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L<EVP_EncryptInit(3)>
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=cut
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