Define hashing of fingerprint

httpwg · Nov 15, 2017 · c90f9b4 · c90f9b4
1 parent d32c533
commit c90f9b4
Showing 1 changed file with 26 additions and 24 deletions.
diff --git a/draft-ietf-httpbis-cache-digest.md b/draft-ietf-httpbis-cache-digest.md
@@ -204,20 +204,21 @@ Given the following inputs:
 4. Let `key` be the return value of {{key}} with `URL` and `ETag` as inputs.
 5. Let `h1` be the return value of {{hash}} with `key` and `N` as inputs.
 6. Let `fingerprint` be the return value of {{fingerprint}} with `key`, `N` and `f` as inputs.
-7. Let `h2` be the return value of {{hash}} with `fingerprint` and `N` as inputs, XORed with `h1`.
-8. Let `h` be either `h1` or `h2`, picked in random.
-9. Let `position_start` be 40 + `h` * `f`.
-10. Let `position_end` be `position_start` + `f` \* `b`.
-11. While `position_start` < `position_end`:
+7. Let `fingerprint-string` be the value of `fingerprint` in base 10, expressed as a string.
+8. Let `h2` be the return value of {{hash}} with `fingerprint-string` and `N` as inputs, XORed with `h1`.
+9. Let `h` be either `h1` or `h2`, picked in random.
+10. Let `position_start` be 40 + `h` * `f`.
+11. Let `position_end` be `position_start` + `f` \* `b`.
+12. While `position_start` < `position_end`:
     1. Let `bits` be `f` bits from `digest_value` starting at `position_start`.
     2. If `bits` is all zeros, set `bits` to `fingerprint` and terminate these steps.
     3. Add `f` to `position_start`.
-12. Substract `f` from `position_start`.
-13. Let `fingerprint` be the `f` bits starting at `position_start`.
-14. Let `h1` be `h`
-15. Substract 1 from `maxcount`.
-16. If `maxcount` is zero, return an error.
-17. Go to step 7.
+13. Substract `f` from `position_start`.
+14. Let `fingerprint` be the `f` bits starting at `position_start`.
+15. Let `h1` be `h`
+16. Substract 1 from `maxcount`.
+17. If `maxcount` is zero, return an error.
+18. Go to step 7.
 
 
 ### Removing a URL to the Digest-Value {#removing}
@@ -234,22 +235,22 @@ Given the following inputs:
 4. Let `key` be the return value of {{key}} with `URL` and `ETag` as inputs.
 5. Let `h1` be the return value of {{hash}} with `key` and `N` as inputs.
 6. Let `fingerprint` be the return value of {{fingerprint}} with `key`, `N` and `f` as inputs.
-7. Let `h2` be the return value of {{hash}} with `fingerprint` and `N` as inputs, XORed with `h1`.
-8. Let `h` be `h1`.
-9. Let `position_start` be 40 + `h` \* `f`.
-10. Let `position_end` be `position_start` + `f` \* `b`.
-11. While `position_start` < `position_end`:
+7. Let `fingerprint-string` be the value of `fingerprint` in base 10, expressed as a string.
+8. Let `h2` be the return value of {{hash}} with `fingerprint-string` and `N` as inputs, XORed with `h1`.
+9. Let `h` be `h1`.
+10. Let `position_start` be 40 + `h` \* `f`.
+11. Let `position_end` be `position_start` + `f` \* `b`.
+12. While `position_start` < `position_end`:
     1. Let `bits` be `f` bits from `digest_value` starting at `position_start`.
     2. If `bits` is `fingerprint`, set `bits` to all zeros and terminate these steps.
     3. Add `f` to `position_start`.
-12. If `h` is not `h2`, set `h` to `h2` and return to step 9.
+13. If `h` is not `h2`, set `h` to `h2` and return to step 9.
 
 ### Computing a fingerprint value {#fingerprint}
 
 Given the following inputs:
 
 * `key`, an array of characters
-* `N`, an integer
 * `f`, an integer indicating the number of output bits
 
 1. Let `hash-value` be the SHA-256 message digest {{RFC6234}} of `key`, expressed as an integer.
@@ -328,15 +329,16 @@ Given the following inputs:
 4. Let `key` be the return value of {{key}} with `URL` and `ETag` as inputs.
 5. Let `h1` be the return value of {{hash}} with `key` and `N` as inputs.
 6. Let `fingerprint` be the return value of {{fingerprint}} with `key`, `N` and `f` as inputs.
-7. Let `h2` be the return value of {{hash}} with `fingerprint` and `N` as inputs, XORed with `h1`.
-8. Let `h` be `h1`.
-9. Let `position_start` be 40 + `h` \* `f`.
-10. Let `position_end` be `position_start` + `f` \* `b`.
-11. While `position_start` < `position_end`:
+7. Let `fingerprint-string` be the value of `fingerprint` in base 10, expressed as a string.
+8. Let `h2` be the return value of {{hash}} with `fingerprint` and `N` as inputs, XORed with `h1`.
+9. Let `h` be `h1`.
+10. Let `position_start` be 40 + `h` \* `f`.
+11. Let `position_end` be `position_start` + `f` \* `b`.
+12. While `position_start` < `position_end`:
     1. Let `bits` be `f` bits from `digest_value` starting at `position_start`.
     2. If `bits` is `fingerprint`, return true
     3. Add `f` to `position_start`.
-12. Return false.
+13. Return false.
 
 # The SENDING_CACHE_DIGEST SETTINGS Parameter