RSA Registers: Difference between revisions
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= Overview = | |||
The RSA module is essentially a hardware-accelerated modular exponentiation engine. It is specially optimized for RSA applications, so its behavior can be incoherent when RSA's invariants are broken. | |||
=== Observed edge cases === | |||
* if 2 divides mod, output == 0 | |||
= Registers = | = Registers = | ||
{| class="wikitable" border="1" | {| class="wikitable" border="1" | ||
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| [[#RSA_EXPFIFO|RSA_EXPFIFO]] | | [[#RSA_EXPFIFO|RSA_EXPFIFO]] | ||
| 0x1000B200 | | 0x1000B200 | ||
| | | 0x100 (can handle u32 writes to any aligned position in the FIFO) | ||
| | | | ||
|- | |- | ||
| Line 71: | Line 78: | ||
|- | |- | ||
| 1 | | 1 | ||
| | | Interrupt enable (1=enable, 0=disable) | ||
|- | |- | ||
| 4-7 | | 4-7 | ||
| Line 77: | Line 84: | ||
|- | |- | ||
| 8 | | 8 | ||
| Endianness (1=Little endian, 0=Big endian) | | Endianness (1=Little endian, 0=Big endian). Affects RSA_EXPFIFO, RSA_MOD, and RSA_TXT. | ||
|- | |- | ||
| 9 | | 9 | ||
| Word order (1=Normal order, 0=Reversed order) | | Word order (1=Normal order, 0=Reversed order). Affects RSA_MOD and RSA_TXT. | ||
|} | |} | ||
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| Key write-protect, this bit is RW. (0 = no protection, 1 = protected) | | Key write-protect, this bit is RW. (0 = no protection, 1 = protected) | ||
|- | |- | ||
| 30- | | 2 | ||
| Key read-protect, this bit is RW. (0 = no protection, 1 = protected) | |||
|- | |||
| 30-3 | |||
| ? | | ? | ||
|- | |- | ||
| 31 | | 31 | ||
| | | Key slot protect. Makes all other bits in this reg read-only until reset | ||
|} | |} | ||
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== RSA_MOD == | == RSA_MOD == | ||
The RSA key modulus for the selected keyslot can be written here. When writing the RSA modulus, the modulus must align with the end of the register area. | The RSA key modulus for the selected keyslot can be written here. When writing the RSA modulus, the modulus must align with the end of the register area. | ||
Writing to RSA_MOD does not change the exponent written with RSA_EXPFIFO. An attack based on the [[wikipedia:Pohlig-Hellman algorithm|Pohlig-Hellman algorithm]] exists to "read" the contents of RSA_EXPFIFO as a result (see [[3DS System Flaws#Hardware|3DS System Flaws]]). | |||
== RSA_TXT == | == RSA_TXT == | ||