Document some preconditions

diff --git a/include/secp256k1.h b/include/secp256k1.h
index cb5fd3c8894abe8d8b8eda88ccfdf7559117d553..4a468e00b2f056e51849896e1da720ff5760c7eb 100644 (file)
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -26,6 +26,12 @@ void secp256k1_stop(void);
  *           0: incorrect signature
  *          -1: invalid public key
  *          -2: invalid signature
+ * In:       msg:       the message being verified (cannot be NULL)
+ *           msglen:    the length of the message (at most 32)
+ *           sig:       the signature being verified (cannot be NULL)
+ *           siglen:    the length of the signature
+ *           pubkey:    the public key to verify with (cannot be NULL)
+ *           pubkeylen: the length of pubkey
  * Requires starting using SECP256K1_START_VERIFY.
  */
 int secp256k1_ecdsa_verify(const unsigned char *msg, int msglen,
@@ -35,12 +41,13 @@ int secp256k1_ecdsa_verify(const unsigned char *msg, int msglen,
 /** Create an ECDSA signature.
  *  Returns: 1: signature created
  *           0: nonce invalid, try another one
- *  In:      msg:    the message being signed
- *           msglen: the length of the message being signed
- *           seckey: pointer to a 32-byte secret key (assumed to be valid)
- *           nonce:  pointer to a 32-byte nonce (generated with a cryptographic PRNG)
- *  Out:     sig:    pointer to a 72-byte array where the signature will be placed.
- *           siglen: pointer to an int, which will be updated to the signature length (<=72).
+ *  In:      msg:    the message being signed (cannot be NULL)
+ *           msglen: the length of the message being signed (at most 32)
+ *           seckey: pointer to a 32-byte secret key (cannot be NULL, assumed to be valid)
+ *           nonce:  pointer to a 32-byte nonce (cannot be NULL, generated with a cryptographic PRNG)
+ *  Out:     sig:    pointer to an array where the signature will be placed (cannot be NULL)
+ *  In/Out:  siglen: pointer to an int with the length of sig, which will be updated
+ *                   to contain the actual signature length (<=72).
  * Requires starting using SECP256K1_START_SIGN.
  */
 int secp256k1_ecdsa_sign(const unsigned char *msg, int msglen,
@@ -51,12 +58,12 @@ int secp256k1_ecdsa_sign(const unsigned char *msg, int msglen,
 /** Create a compact ECDSA signature (64 byte + recovery id).
  *  Returns: 1: signature created
  *           0: nonce invalid, try another one
- *  In:      msg:    the message being signed
- *           msglen: the length of the message being signed
- *           seckey: pointer to a 32-byte secret key (assumed to be valid)
- *           nonce:  pointer to a 32-byte nonce (generated with a cryptographic PRNG)
- *  Out:     sig:    pointer to a 64-byte array where the signature will be placed.
- *           recid:  pointer to an int, which will be updated to contain the recovery id.
+ *  In:      msg:    the message being signed (cannot be NULL)
+ *           msglen: the length of the message being signed (at most 32)
+ *           seckey: pointer to a 32-byte secret key (cannot be NULL, assumed to be valid)
+ *           nonce:  pointer to a 32-byte nonce (cannot be NULL, generated with a cryptographic PRNG)
+ *  Out:     sig:    pointer to a 64-byte array where the signature will be placed (cannot be NULL)
+ *           recid:  pointer to an int, which will be updated to contain the recovery id (can be NULL)
  * Requires starting using SECP256K1_START_SIGN.
  */
 int secp256k1_ecdsa_sign_compact(const unsigned char *msg, int msglen,
@@ -66,15 +73,15 @@ int secp256k1_ecdsa_sign_compact(const unsigned char *msg, int msglen,
                                  int *recid);
 
 /** Recover an ECDSA public key from a compact signature.
- *  Returns: 1: public key succesfully recovered (which guarantees a correct signature).
+ *  Returns: 1: public key successfully recovered (which guarantees a correct signature).
  *           0: otherwise.
- *  In:      msg:        the message assumed to be signed
- *           msglen:     the length of the message
- *           sig64:      signature as 64 byte array
+ *  In:      msg:        the message assumed to be signed (cannot be NULL)
+ *           msglen:     the length of the message (at most 32)
+ *           sig64:      signature as 64 byte array (cannot be NULL)
  *           compressed: whether to recover a compressed or uncompressed pubkey
- *           recid:      the recovery id (as returned by ecdsa_sign_compact)
- *  Out:     pubkey:     pointer to a 33 or 65 byte array to put the pubkey.
- *           pubkeylen:  pointer to an int that will contain the pubkey length.
+ *           recid:      the recovery id (0-3, as returned by ecdsa_sign_compact)
+ *  Out:     pubkey:     pointer to a 33 or 65 byte array to put the pubkey (cannot be NULL)
+ *           pubkeylen:  pointer to an int that will contain the pubkey length (cannot be NULL)
  * Requires starting using SECP256K1_START_VERIFY.
  */
 int secp256k1_ecdsa_recover_compact(const unsigned char *msg, int msglen,
@@ -85,23 +92,25 @@ int secp256k1_ecdsa_recover_compact(const unsigned char *msg, int msglen,
 /** Verify an ECDSA secret key.
  *  Returns: 1: secret key is valid
  *           0: secret key is invalid
- *  In:      seckey: pointer to a 32-byte secret key
+ *  In:      seckey: pointer to a 32-byte secret key (cannot be NULL)
  */
 int secp256k1_ec_seckey_verify(const unsigned char *seckey);
 
 /** Just validate a public key.
  *  Returns: 1: valid public key
  *           0: invalid public key
+ *  In:      pubkey:    pointer to a 33-byte or 65-byte public key (cannot be NULL).
+ *           pubkeylen: length of pubkey
  */
 int secp256k1_ec_pubkey_verify(const unsigned char *pubkey, int pubkeylen);
 
 /** Compute the public key for a secret key.
  *  In:     compressed: whether the computed public key should be compressed
- *          seckey:     pointer to a 32-byte private key.
+ *          seckey:     pointer to a 32-byte private key (cannot be NULL)
  *  Out:    pubkey:     pointer to a 33-byte (if compressed) or 65-byte (if uncompressed)
- *                      area to store the public key.
+ *                      area to store the public key (cannot be NULL)
  *          pubkeylen:  pointer to int that will be updated to contains the pubkey's
- *                      length.
+ *                      length (cannot be NULL)
  *  Returns: 1: secret was valid, public key stores
  *           0: secret was invalid, try again.
  * Requires starting using SECP256K1_START_SIGN.
@@ -110,8 +119,8 @@ int secp256k1_ec_pubkey_create(unsigned char *pubkey, int *pubkeylen, const unsi
 
 /** Decompress a public key.
  * In/Out: pubkey:    pointer to a 65-byte array to put the decompressed public key.
-                      It must contain a 33-byte or 65-byte public key already.
- *         pubkeylen: pointer to the size of the public key pointed to be pubkey.
+                      It must contain a 33-byte or 65-byte public key already (cannot be NULL)
+ *         pubkeylen: pointer to the size of the public key pointed to by pubkey (cannot be NULL)
                       It will be updated to reflect the new size.
  * Returns: 0 if the passed public key was invalid, 1 otherwise. If 1 is returned, the
             pubkey is replaced with its decompressed version.