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Merge #710: Eliminate harmless non-constant time operations on secret data.

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7b50483ad7 Adds a declassify operation to aid constant-time analysis. (Gregory Maxwell)
34a67c773b Eliminate harmless non-constant time operations on secret data. (Gregory Maxwell)

Pull request description:

  There were several places where the code was non-constant time
   for invalid secret inputs.  These are harmless under sane use
   but get in the way of automatic const-time validation.

  (Nonce overflow in signing is not addressed, nor is s==0 in signing)

ACKs for top commit:
  sipa:
    utACK 7b50483ad7
  real-or-random:
    ACK 7b50483ad7 I read the code carefully and tested it
  jonasnick:
    reACK 7b50483ad7

Tree-SHA512: 0776c3a86e723d2f97b9b9cb31d0d0e59dfcf308093b3f46fbc859f73f9957f3fa977d03b57727232040368d058701ef107838f9b1ec98f925ec78ddad495c4e
This commit is contained in:
Tim Ruffing
2020-02-24 14:02:44 +01:00
parent 0585b8b2ee 7b50483ad7
commit 96d8ccbd16
20 changed files with 194 additions and 111 deletions
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2
include/secp256k1.h
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@@ -162,12 +162,14 @@ typedef int (*secp256k1_nonce_function)(
/** The higher bits contain the actual data. Do not use directly. */
#define SECP256K1_FLAGS_BIT_CONTEXT_VERIFY (1 << 8)
#define SECP256K1_FLAGS_BIT_CONTEXT_SIGN (1 << 9)
#define SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY (1 << 10)
#define SECP256K1_FLAGS_BIT_COMPRESSION (1 << 8)
/** Flags to pass to secp256k1_context_create, secp256k1_context_preallocated_size, and
* secp256k1_context_preallocated_create. */
#define SECP256K1_CONTEXT_VERIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_VERIFY)
#define SECP256K1_CONTEXT_SIGN (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_SIGN)
#define SECP256K1_CONTEXT_DECLASSIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY)
#define SECP256K1_CONTEXT_NONE (SECP256K1_FLAGS_TYPE_CONTEXT)
/** Flag to pass to secp256k1_ec_pubkey_serialize. */