Random Number Algorithm Definitions¶
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struct
rng_alg¶ random number generator definition
Definition
struct rng_alg {
int (* generate) (struct crypto_rng *tfm,const u8 *src, unsigned int slen, u8 *dst, unsigned int dlen);
int (* seed) (struct crypto_rng *tfm, const u8 *seed, unsigned int slen);
void (* set_ent) (struct crypto_rng *tfm, const u8 *data, unsigned int len);
unsigned int seedsize;
struct crypto_alg base;
};
Members
generate- The function defined by this variable obtains a random number. The random number generator transform must generate the random number out of the context provided with this call, plus any additional data if provided to the call.
seed- Seed or reseed the random number generator. With the invocation of this function call, the random number generator shall become ready for generation. If the random number generator requires a seed for setting up a new state, the seed must be provided by the consumer while invoking this function. The required size of the seed is defined with seedsize .
set_ent- Set entropy that would otherwise be obtained from entropy source. Internal use only.
seedsize- The seed size required for a random number generator initialization defined with this variable. Some random number generators does not require a seed as the seeding is implemented internally without the need of support by the consumer. In this case, the seed size is set to zero.
base- Common crypto API algorithm data structure.
Crypto API Random Number API¶
The random number generator API is used with the ciphers of type CRYPTO_ALG_TYPE_RNG (listed as type “rng” in /proc/crypto)
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struct crypto_rng *
crypto_alloc_rng(const char * alg_name, u32 type, u32 mask)¶ - allocate RNG handle
Parameters
const char * alg_name- is the cra_name / name or cra_driver_name / driver name of the message digest cipher
u32 type- specifies the type of the cipher
u32 mask- specifies the mask for the cipher
Description
Allocate a cipher handle for a random number generator. The returned struct crypto_rng is the cipher handle that is required for any subsequent API invocation for that random number generator.
For all random number generators, this call creates a new private copy of
the random number generator that does not share a state with other
instances. The only exception is the “krng” random number generator which
is a kernel crypto API use case for the get_random_bytes() function of the
/dev/random driver.
Return
- allocated cipher handle in case of success;
IS_ERR()is true in case - of an error,
PTR_ERR()returns the error code.
Parameters
struct crypto_rng * tfm- cipher handle
Description
Return the generic name (cra_name) of the initialized random number generator
Return
generic name string
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void
crypto_free_rng(struct crypto_rng * tfm)¶ zeroize and free RNG handle
Parameters
struct crypto_rng * tfm- cipher handle to be freed
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int
crypto_rng_generate(struct crypto_rng * tfm, const u8 * src, unsigned int slen, u8 * dst, unsigned int dlen)¶ get random number
Parameters
struct crypto_rng * tfm- cipher handle
const u8 * src- Input buffer holding additional data, may be NULL
unsigned int slen- Length of additional data
u8 * dst- output buffer holding the random numbers
unsigned int dlen- length of the output buffer
Description
This function fills the caller-allocated buffer with random numbers using the random number generator referenced by the cipher handle.
Return
0 function was successful; < 0 if an error occurred
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int
crypto_rng_get_bytes(struct crypto_rng * tfm, u8 * rdata, unsigned int dlen)¶ get random number
Parameters
struct crypto_rng * tfm- cipher handle
u8 * rdata- output buffer holding the random numbers
unsigned int dlen- length of the output buffer
Description
This function fills the caller-allocated buffer with random numbers using the random number generator referenced by the cipher handle.
Return
0 function was successful; < 0 if an error occurred
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int
crypto_rng_reset(struct crypto_rng * tfm, const u8 * seed, unsigned int slen)¶ re-initialize the RNG
Parameters
struct crypto_rng * tfm- cipher handle
const u8 * seed- seed input data
unsigned int slen- length of the seed input data
Description
The reset function completely re-initializes the random number generator referenced by the cipher handle by clearing the current state. The new state is initialized with the caller provided seed or automatically, depending on the random number generator type (the ANSI X9.31 RNG requires caller-provided seed, the SP800-90A DRBGs perform an automatic seeding). The seed is provided as a parameter to this function call. The provided seed should have the length of the seed size defined for the random number generator as defined by crypto_rng_seedsize.
Return
0 if the setting of the key was successful; < 0 if an error occurred
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int
crypto_rng_seedsize(struct crypto_rng * tfm)¶ obtain seed size of RNG
Parameters
struct crypto_rng * tfm- cipher handle
Description
The function returns the seed size for the random number generator referenced by the cipher handle. This value may be zero if the random number generator does not implement or require a reseeding. For example, the SP800-90A DRBGs implement an automated reseeding after reaching a pre-defined threshold.
Return
seed size for the random number generator