fix modulus length, as encoded in COSE_Key, to be 256 bytes rather th…

…an 257

index.bs

@@ -2563,7 +2563,7 @@ to be used with the PS256 signature algorithm
   {
      1:  3,  ; kty: RSA key type
      3:-37,  ; alg: PS256
-    -1:  n,  ; n:   RSA modulus n byte string 257 bytes in length
+    -1:  n,  ; n:   RSA modulus n byte string 256 bytes in length
                     e.g., in hex (middle bytes elided for brevity): DB5F651550...6DC6548ACC3
     -2:  e   ; e:   RSA public exponent e byte string 3 bytes in length
                     e.g., in hex: 010001
@@ -2578,7 +2578,7 @@ to be used with the RS256 signature algorithm (RSASSA-PKCS1-v1_5 w/ SHA-256, see
   {
      1:   3,  ; kty: RSA key type
      3:-257,  ; alg: RS256
-    -1:  n,  ; n:   RSA modulus n byte string 257 bytes in length
+    -1:  n,  ; n:   RSA modulus n byte string 256 bytes in length
                     e.g., in hex (middle bytes elided for brevity): DB5F651550...6DC6548ACC3
     -2:  e   ; e:   RSA public exponent e byte string 3 bytes in length
                     e.g., in hex: 010001