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Remove EEPROM address argument from RNG.begin()

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Always store the seed at the very end of EEPROM memory.
This commit is contained in:
Rhys Weatherley
2017-11-04 10:18:05 +10:00
parent 506af269b7
commit d452bea037
9 changed files with 32 additions and 39 deletions
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23
doc/crypto-rng.dox
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@@ -133,8 +133,8 @@ all of the application's noise sources:
\code
void setup() {
// Initialize the random number generator with the application tag
// "MyApp 1.0" and load the previous seed from EEPROM address 950.
RNG.begin("MyApp 1.0", 950);
// "MyApp 1.0" and load the previous seed from EEPROM.
RNG.begin("MyApp 1.0");
// Add the noise source to the list of sources known to RNG.
RNG.addNoiseSource(noise);
@@ -143,17 +143,16 @@ void setup() {
}
\endcode
The begin() function is passed two arguments: a tag string that should
be different for every application and an EEPROM address to use to
load and save the random number seed. The tag string ensures that
different applications and versions will generate different random numbers
upon first boot before the noise source has collected any entropy.
If the device also has a unique serial number or a MAC address, then
those can be mixed in during the setup() function after calling begin():
The begin() function is passed a tag string that should be different for
every application. The tag string ensures that different applications and
versions will generate different random numbers upon first boot before
the noise source has collected any entropy. If the device also has a unique
serial number or a MAC address, then those can be mixed in during the
setup() function after calling begin():
\code
void setup() {
RNG.begin("MyApp 1.0", 950);
RNG.begin("MyApp 1.0");
RNG.stir(serial_number, sizeof(serial_number));
RNG.stir(mac_address, sizeof(mac_address));
RNG.addNoiseSource(noise);
@@ -161,8 +160,8 @@ void setup() {
}
\endcode
The random number generator needs 49 bytes of EEPROM space at the
specified address to store the previous seed. When the system is started
The random number generator uses 49 bytes of space at the end of
EEPROM memory to store the previous seed. When the system is started
next time, the previous saved seed is loaded and then deliberately
overwritten with a new seed. This ensures that the device will not
accidentally generate the same sequence of random numbers if it is