[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Minor suggestions for draft-metzger-esp-des-cbc-01.txt
Here are some changes I propose for -esp-des-cbc-01.
j'
diff draft-metzger-esp-des-cbc-01.txt draft-metzger-esp-des-cbc-01.txt.ala.jpp
177,179c177,179
< The field may be longer or shorter than the 64-bits used by DES,
< in multiples of 32-bits. This allows alignment of the Encrypted
< Data for in-place decryption.
---
> Although the field must be a multiple of 32-bits long, it may be
> longer or shorter than the 64-bits used by DES. This allows
> alignment of the Encrypted Data for in-place decryption.
[english]
189,190c189,194
< When the size is negotiated to 32-bits, the inverse of the 32-bits
< is appended to form a 64-bit value.
---
> When the size is negotiated to 32-bits, the inverse of the 32-bit
> field value is folowed by the 32-bit field value to form the
> 64-bit IV. A fragment of C code which computes this function is
> "iv64= ((~ iv32) << 32) | iv32;" Where iv32, and iv64 are
> declared to be 64 (or more) bit integers, and the IV is the least
> significant 64 bits of iv64.
[Be sure to spell it out clearly enough to be implemented. For
convienience in the C code, I (might have (but I am not compleately
sure (see the problem?))) re-ordered the halves of the IV.]
191a196,201
> When the size is negotiated to be 64-bits, the 64 bits field
> value is used as the 64 bit initialization vector. The vector is
> created according to a "big-endian" convention; i.e. the first
> octet becomes bits 1-8 of the IV, and the last octet becomes bits
> 57-64 of the IV.
>
[still spelling the obvious out, just to be sure. The big-endian
stuff should be stuck on each of the paragraphs, or factored out to a
final paragraph somehow.]
193,194c203,204
< of the 64-bit value within this field is negotiated by an |
< additional parameter. Unused octets are filled with unspecified |
---
> of the 64-bit IV within this field is negotiated by an additional |
> parameter. Unused octets are filled with unspecified |
[english -- keep the name of the IV consistent]
252,253c262,263
< Append zero or more octets of padding to the plain text, to make |
< its length in octets modulo 8 equal to 6. |
---
> Append zero or more octets of padding to the plain text, to make its |
> length in octets equal to 8i + 6, for some integer i greater than 0. |
[I thought mathematicians would say "equal to 6 modulo 8", but
computer programmers would say "modulo 8 equal to 6". I hope both can
read my version without confusion]
261,262c271
< Encrypt the payload with DES in CBC mode, producing a cipher text of |
< the same length. |
---
> Compute an initialization vector apropriate to the SAID. |
263a273,275
> Encrypt the payload with DES in CBC mode using the computed |
> initialization value, producing a cipher text of the same length. |
>
[Don't forget to make, and use, the IV]
308a321
> [Are these last two correct for both IP-Mode and Transport-Mode?]
[re: changing the value of the IP length, and 'delivering' the result.]
341c354
< a better choice for such purposes.
---
> a better choice for such purposes. [reference -esp-3des.txt perhaps?]
[Would be nice. Would be nice to have such a doc. :) ]