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Clarify documentation of tweak functions.
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In particular, mention that the functions return 0 if seckey or tweak are
invalid (as opposed to saying "should" or "must" be valid).
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@jonasnick
jonasnick committed Mar 30, 2020
1 parent 89853a0 commit 7e3952a
Showing 1 changed file with 46 additions and 41 deletions.
87 changes: 46 additions & 41 deletions include/secp256k1.h
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Original file line number Diff line number Diff line change
Expand Up @@ -586,11 +586,12 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
*
* Returns: 0 if the given secret key is invalid according to
* secp256k1_ec_seckey_verify. 1 otherwise
* Args: ctx: pointer to a context object
* In/Out: seckey: pointer to the 32-byte secret key to be negated. The secret
* key should be valid according to secp256k1_ec_seckey_verify.
* If this function returns 0, seckey will be some
* unspecified value. (cannot be NULL)
* Args: ctx: pointer to a context object
* In/Out: seckey: pointer to the 32-byte secret key to be negated. If the
* secret key is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0 and
* seckey will be set to some unspecified value. (cannot be
* NULL)
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_negate(
const secp256k1_context* ctx,
Expand All @@ -617,17 +618,18 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate(

/** Tweak a secret key by adding tweak to it.
*
* Returns: 0 if the resulting secret key would be invalid (only when the tweak
* is the negation of the secret key). 1 otherwise.
* Args: ctx: pointer to a context object (cannot be NULL).
* In/Out: seckey: pointer to a 32-byte secret key. The secret key should be
* valid according to secp256k1_ec_seckey_verify. If this
* function returns 0, seckey will be some unspecified
* value. (cannot be NULL)
* In: tweak: pointer to a 32-byte tweak. Must be in the same range as secret
* keys (see secp256k1_ec_seckey_verify). For uniformly random
* 32-byte arrays the chance of being out of range is
* negligible (around 1 in 2^128). (cannot be NULL)
* Returns: 0 if the arguments are invalid or the resulting secret key would be
* invalid (only when the tweak is the negation of the secret key). 1
* otherwise.
* Args: ctx: pointer to a context object (cannot be NULL).
* In/Out: seckey: pointer to a 32-byte secret key. If the secret key is
* invalid according to secp256k1_ec_seckey_verify, this
* function returns 0. seckey will be set to some unspecified
* value if this function returns 0. (cannot be NULL)
* In: tweak: pointer to a 32-byte tweak. If the tweak is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0. For
* uniformly random 32-byte arrays the chance of being invalid
* is negligible (around 1 in 2^128) (cannot be NULL).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_add(
const secp256k1_context* ctx,
Expand All @@ -645,16 +647,17 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add(

/** Tweak a public key by adding tweak times the generator to it.
*
* Returns: 0 if the resulting public key would be invalid (only when the tweak
* is the negation of the corresponding secret key). 1 otherwise.
* Args: ctx: pointer to a context object initialized for validation
* (cannot be NULL).
* In/Out: pubkey: pointer to a public key object. If this function returns 0,
* pubkey will be invalid. (cannot be NULL).
* In: tweak: pointer to a 32-byte tweak. Must be in the same range as secret
* keys (see secp256k1_ec_seckey_verify). For uniformly random
* 32-byte arrays the chance of being out of range is
* negligible (around 1 in 2^128). (cannot be NULL)
* Returns: 0 if the arguments are invalid or the resulting public key would be
* invalid (only when the tweak is the negation of the corresponding
* secret key). 1 otherwise.
* Args: ctx: pointer to a context object initialized for validation
* (cannot be NULL).
* In/Out: pubkey: pointer to a public key object. pubkey will be set to an
* invalid value if this function returns 0 (cannot be NULL).
* In: tweak: pointer to a 32-byte tweak. If the tweak is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0. For
* uniformly random 32-byte arrays the chance of being invalid
* is negligible (around 1 in 2^128) (cannot be NULL).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(
const secp256k1_context* ctx,
Expand All @@ -664,14 +667,16 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(

/** Tweak a secret key by multiplying it by a tweak.
*
* Returns: 0 if the arguments are invalid.. 1 otherwise.
* Returns: 0 if the arguments are invalid. 1 otherwise.
* Args: ctx: pointer to a context object (cannot be NULL).
* In/Out: seckey: pointer to a 32-byte secret key. If this function returns 0,
* seckey will be some unspecified value. (cannot be NULL).
* In: tweak: pointer to a 32-byte tweak. Must be in the same range as secret
* keys (see secp256k1_ec_seckey_verify). For uniformly random
* 32-byte arrays the chance of being out of range is
* negligible (around 1 in 2^128). (cannot be NULL)
* In/Out: seckey: pointer to a 32-byte secret key. If the secret key is
* invalid according to secp256k1_ec_seckey_verify, this
* function returns 0. seckey will be set to some unspecified
* value if this function returns 0. (cannot be NULL)
* In: tweak: pointer to a 32-byte tweak. If the tweak is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0. For
* uniformly random 32-byte arrays the chance of being invalid
* is negligible (around 1 in 2^128) (cannot be NULL).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_mul(
const secp256k1_context* ctx,
Expand All @@ -690,14 +695,14 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(
/** Tweak a public key by multiplying it by a tweak value.
*
* Returns: 0 if the arguments are invalid. 1 otherwise.
* Args: ctx: pointer to a context object initialized for validation
* (cannot be NULL).
* In/Out: pubkey: pointer to a public key object. If this function returns 0,
* pubkey will be invalid. (cannot be NULL).
* In: tweak: pointer to a 32-byte tweak. Must be in the same range as secret
* keys (see secp256k1_ec_seckey_verify). For uniformly random
* 32-byte arrays the chance of being out of range is
* negligible (around 1 in 2^128). (cannot be NULL)
* Args: ctx: pointer to a context object initialized for validation
* (cannot be NULL).
* In/Out: pubkey: pointer to a public key object. pubkey will be set to an
* invalid value if this function returns 0 (cannot be NULL).
* In: tweak: pointer to a 32-byte tweak. If the tweak is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0. For
* uniformly random 32-byte arrays the chance of being invalid
* is negligible (around 1 in 2^128) (cannot be NULL).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(
const secp256k1_context* ctx,
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