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Corrected. It said before that ivec had to be initialised to zero,

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which isn't true.  What is true, however, is that SSH assumes it is.
This commit is contained in:
Richard Levitte 2000-03-23 11:08:49 +00:00
parent 87351c586e
commit 1bb30673f9
1 changed files with 9 additions and 6 deletions
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15
doc/crypto/blowfish.pod
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@ -57,28 +57,31 @@ everything after the first 64 bits is ignored.
The mode functions BF_cbc_encrypt(), BF_cfb64_encrypt() and BF_ofb64_encrypt()
all operate on variable length data. They all take an initialisation vector
B<ivec> which must be initially filled with zeros, but then just need to be
passed along into the next call of the same function for the same message.
B<ivec> which needs to be passed along into the next call of the same function
for the same message. B<ivec> may be initialised with anything, but the
recipient needs to know what it was initialised with, or it won't be able
to decrypt. Some programs and protocols simplify this, like SSH, where
B<ivec> is simply initialised to zero.
BF_cbc_encrypt() operates of data that is a multiple of 8 bytes long, while
BF_cfb64_encrypt() and BF_ofb64_encrypt() are used to encrypt an variable
number of bytes (the amount does not have to be an exact multiple of 8). The
purpose of the latter two is to simulate stream ciphers, and therefore, they
need the parameter B<num>, which is a pointer to an integer where the current
offset in B<ivec> is stored between calls. This integer must be initialised
to zero when B<ivec> is filled with zeros.
to zero when B<ivec> is initialised.
BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish. It
encrypts or decrypts the 64 bits chunks of B<in> using the key B<schedule>,
putting the result in B<out>. B<enc> decides if encryption (BF_ENCRYPT) or
decryption (BF_DECRYPT) shall be performed. B<ivec> must point at an 8 byte
long initialisation vector, which must be initially filled with zeros.
long initialisation vector.
BF_cfb64_encrypt() is the CFB mode for Blowfish with 64 bit feedback.
It encrypts or decrypts the bytes in B<in> using the key B<schedule>,
putting the result in B<out>. B<enc> decides if encryption (B<BF_ENCRYPT>)
or decryption (B<BF_DECRYPT>) shall be performed. B<ivec> must point at an
8 byte long initialisation vector, which must be initially filled with zeros.
B<num> must point at an integer which must be initially zero.
8 byte long initialisation vector. B<num> must point at an integer which must
be initially zero.
BF_ofb64_encrypt() is the OFB mode for Blowfish with 64 bit feedback.
It uses the same parameters as BF_cfb64_encrypt(), which must be initialised