From cac0b07415a610cde2571a6db4e63acab3f68049 Mon Sep 17 00:00:00 2001
From: David Florness <david@florness.com>
Date: Sun, 9 Feb 2020 21:15:58 -0700
Subject: [PATCH] The client can deduce the constant from the sums!

---
 client.rkt | 58 +++++++++++++++++++++++++++++++++---------------------
 1 file changed, 36 insertions(+), 22 deletions(-)

diff --git a/client.rkt b/client.rkt
index 1e26a4d..1341053 100644
--- a/client.rkt
+++ b/client.rkt
@@ -1,16 +1,18 @@
 #lang racket/base
-(require racket/port)
+(require math/matrix)
 (require racket/contract)
+(require racket/list)
 (require racket/math)
+(require racket/port)
 
-(require readline/readline)
+(require (only-in openssl/sha1 hex-string->bytes))
+(require binaryio)
 (require crypto)
+(require json)
 (require net/http-client)
 (require net/uri-codec)
-(require json)
-(require binaryio)
+(require readline/readline)
 (require simple-http)
-(require (only-in openssl/sha1 hex-string->bytes))
 
 (define num-bytes (/ 1024 8))
 
@@ -118,21 +120,33 @@
                                         (natural->hex-string point))))))))))))))
   (newline)
 
-  (display "summing sums...")
-  (define sum
-    (foldl + 0
-           (map
-            hex-string->natural
-            (hash-values
-             (json-response-body
-              (let loop ([wait 0])
-                (sleep wait)
-                (with-handlers ([exn:fail:network:http:error?
-                                 (λ (exn)
-                                   (break-enabled #t)
-                                   (display ".")
-                                   (flush-output)
-                                   (loop 3))])
-                  (get bulletin "/sums"))))))))
+  (display "finding constant...")
+  (define constant
+    (let ([k (length peer-inputs)]
+          [sums (for/hash ([(k v)
+                            (in-hash
+                             (json-response-body
+                              (let loop ([wait 0])
+                                (sleep wait)
+                                (with-handlers ([exn:fail:network:http:error?
+                                                 (λ (exn)
+                                                   (break-enabled #t)
+                                                   (display ".")
+                                                   (flush-output)
+                                                   (loop 3))])
+                                  (get bulletin "/sums")))))])
+                  (values (hex-string->natural (symbol->string k))
+                          (hex-string->natural v)))])
+      (matrix-ref
+       (matrix-solve
+        ; M
+        (for*/matrix k k ([x peer-inputs]
+                          [p (range k)])
+                     (expt x p))
+        ; B
+        (for*/matrix k 1 ([x peer-inputs])
+                     (hash-ref sums x)))
+       0 0)))
   (newline)
-  (displayln (format "sum: ~a" sum)))
+
+  (displayln (format "Result: ~a" constant)))
-- 
2.38.4