From 09436d4df6333a54b3248f2075436c79b5e56a0d Mon Sep 17 00:00:00 2001
From: davidsarah <>
Date: Wed, 11 Jan 2012 21:51:12 +0000
Subject: [PATCH] add example of 306-bit (2K+T) caps

[Imported from Trac: page NewMutableEncodingDesign, version 23]
---
 NewMutableEncodingDesign.md | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/NewMutableEncodingDesign.md b/NewMutableEncodingDesign.md
index c704288..5b4a801 100644
--- a/NewMutableEncodingDesign.md
+++ b/NewMutableEncodingDesign.md
@@ -62,17 +62,20 @@ A likely security parameter K (=kappa) would be 128 bits.
 Assuming a `lafs:` prefix and no additional metadata, here's what
 various lengths of base62-encoded filecaps would look like:
 
- * K+T:
-  * 128+50 `lafs:3zusfONRfEOp17B0ad2TDDSJxtBpvH`
- * 2*K:
-  * 256 `lafs:fZeioazoWrO62reiAjzUAyV0uz3ssh6Hnanv8cKMClY`
- * 3*K:
-  * 384 `lafs:3a31SqUbf8fpWE1opRCT3coDhRqTU7bDU2AvC3RQJBu6ZNFhVscyxA9slYtPVT79x`
+ * K + T = 178:
+  * `lafs:3zusfONRfEOp17B0ad2TDDSJxtBpvH`
+ * 2*K = 256:
+  * `lafs:fZeioazoWrO62reiAjzUAyV0uz3ssh6Hnanv8cKMClY`
+ * 2*K + T = 306:
+  * `lafs:2s1SqUbf8fpsh6HnThRqTUtBpvH7D8fpWEDSfZeioazoWrO62rei`
+ * 3*K = 384:
+  * `lafs:3a31SqUbf8fpWE1opRCT3coDhRqTU7bDU2AvC3RQJBu6ZNFhVscyxA9slYtPVT79x`
 
 Adding 2 metadata characters and a clear separator gives us:
 
- * 128+50 `lafs:DW-3zusfONRfEOp17B0ad2TDDSJxtBpvH`
+ * 178 `lafs:DW-3zusfONRfEOp17B0ad2TDDSJxtBpvH`
  * 256: `lafs:DR-fZeioazoWrO62reiAjzUAyV0uz3ssh6Hnanv8cKMClY`
+ * 306: `lafs:DR-2s1SqUbf8fpsh6HnThRqTUtBpvH7D8fpWEDSfZeioazoWrO62rei`
  * 384: `lafs:DV-3a31SqUbf8fpWE1opRCT3coDhRqTU7bDU2AvC3RQJBu6ZNFhVscyxA9slYtPVT79x`
 
 [#217:c44]comment:44:[/tahoe-lafs/trac-2024-07-25/issues/7722](/tahoe-lafs/trac-2024-07-25/issues/7722) says that, if we don't need to prevent collisions, then we can use a K-bit hash for K-bit second-pre-image resistance. However, see [#882:c6]comment:6:[/tahoe-lafs/trac-2024-07-25/issues/8387](/tahoe-lafs/trac-2024-07-25/issues/8387) for a counterargument saying that 50 extra bits or so are needed to be secure against multi-target attacks (i.e. T = 50). This page has now been updated assuming the counterargument is correct.