Prng C Reference Documentation
Prng
Current Version: 10.1.0
Provides secure pseudo-random number generation (PRNG). Implements the Fortuna PRNG algorithm using 256-bit AES and SHA256. Also provides methods for accessing sources of system entropy.
Create/Dispose
HCkPrng instance = CkPrng_Create(); // ... CkPrng_Dispose(instance);
Creates an instance of the HCkPrng object and returns a handle ("void *" pointer). The handle is passed in the 1st argument for the functions listed on this page.
Objects created by calling CkPrng_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function. Also, any handle returned by a Chilkat "C" function must also be freed by the application by calling the appropriate Dispose method, such as CkPrng_Dispose.
Properties
DebugLogFilePath
void CkPrng_putDebugLogFilePath(HCkPrng cHandle, const char *newVal);
const char *CkPrng_debugLogFilePath(HCkPrng cHandle);
If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.
This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:
- a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
- the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
- there is an internal problem (bug) in the Chilkat code that causes the hang.
LastErrorHtml
const char *CkPrng_lastErrorHtml(HCkPrng cHandle);
Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.
topLastErrorText
const char *CkPrng_lastErrorText(HCkPrng cHandle);
Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.
LastErrorXml
const char *CkPrng_lastErrorXml(HCkPrng cHandle);
Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.
topLastMethodSuccess
void CkPrng_putLastMethodSuccess(HCkPrng cHandle, BOOL newVal);
Indicate whether the last method call succeeded or failed. A value of TRUE indicates success, a value of FALSE indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:
- Any method that returns a string.
- Any method returning a Chilkat object, binary bytes, or a date/time.
- Any method returning a standard boolean status value where success = TRUE and failure = FALSE.
- Any method returning an integer where failure is defined by a return value less than zero.
Note: Methods that do not fit the above requirements will always set this property equal to TRUE. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.
topPrngName
void CkPrng_putPrngName(HCkPrng cHandle, const char *newVal);
const char *CkPrng_prngName(HCkPrng cHandle);
The name of the PRNG selected. Currently, the default and only possible value is "fortuna". See the links below for information about the Fortuna PRNG.
Note: Because "fortuna" is the only valid choice, assigning this property to a different value will always be ignored (until alternative PRNG algorithms are added in the future).
Utf8
void CkPrng_putUtf8(HCkPrng cHandle, BOOL newVal);
When set to TRUE, all "const char *" arguments are interpreted as utf-8 strings. If set to FALSE (the default), then "const char *" arguments are interpreted as ANSI strings. Also, when set to TRUE, and Chilkat method returning a "const char *" is returning the utf-8 representation. If set to FALSE, all "const char *" return values are ANSI strings.
topVerboseLogging
void CkPrng_putVerboseLogging(HCkPrng cHandle, BOOL newVal);
If set to TRUE, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is FALSE. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
topVersion
const char *CkPrng_version(HCkPrng cHandle);
Methods
AddEntropy
Adds entropy to the PRNG (i.e. adds more seed material to the PRNG). Entropy can be obtained by calling GetEntropy, or the application might have its own sources for obtaining entropy. An application may continue to add entropy at desired intervals. How the entropy is used depends on the PRNG algorithm. For Fortuna, the entropy is added to the internal entropy pools and used when internal automatic reseeding occurs.
An application may add non-random entropy for testing purposes. This allows for the reproduction of the same pseudo-random number sequence for testing and debugging purposes.
The entropy bytes are passed in entropy using the binary encoding specified in encoding. Binary encodings can be "hex", "base64", etc. See the link below for supported binary encodings.
Returns TRUE for success, FALSE for failure.
AddEntropyBytes
Adds entropy to the PRNG (i.e. adds more seed material to the PRNG). Entropy can be obtained by calling GetEntropy, or the application might have its own sources for obtaining entropy. An application may continue to add entropy at desired intervals. How the entropy is used depends on the PRNG algorithm. For Fortuna, the entropy is added to the internal entropy pools and used when internal automatic reseeding occurs.
An application may add non-random entropy for testing purposes. This allows for the reproduction of the same pseudo-random number sequence for testing and debugging purposes.
Returns TRUE for success, FALSE for failure.
topExportEntropy
const char *CkPrng_exportEntropy(HCkPrng cHandle);
Exports all accumulated entropy and returns it in a base64 encoded string. (Internally the entropy pools are re-hashed so that a hacker cannot determine the state of the PRNG even if the exported entropy was obtained.) When a system restarts it can import what was previously exported by calling ImportEntropy. This ensures an adequate amount of entropy is immediately available when first generating random bytes.
For example, an application could persist the exported entropy to a database or file. When the application starts again, it could import the persisted entropy, add some entropy from a system source (via the GetEntropy/AddEntropy methods), and then begin generating random data.
Returns TRUE for success, FALSE for failure.
FirebasePushId
const char *CkPrng_firebasePushId(HCkPrng cHandle);
Generates a random Firebase Push ID. See Firebase Unique Identifiers.
Returns TRUE for success, FALSE for failure.
GenRandom
const char *CkPrng_genRandom(HCkPrng cHandle, int numBytes, const char *encoding);
Generates and returns numBytes random bytes in encoded string form. The binary encoding is specified by encoding, and can be "hex", "base64", etc. (See the link below for supported binary encodings.)
Important: If no entropy was explicitly added prior to first call to generate random bytes, then 32 bytes of entropy (from the system source, such as /dev/random) are automatically added to seed the PRNG.
Returns TRUE for success, FALSE for failure.
GenRandomBd
Appends numBytes random bytes to bd.
Important: If no entropy was explicitly added prior to first call to generate random bytes, then 32 bytes of entropy (from the system source, such as /dev/random) are automatically added to seed the PRNG.
Returns TRUE for success, FALSE for failure.
GenRandomBytes
Generates and returns numBytes random bytes.
Important: If no entropy was explicitly added prior to first call to generate random bytes, then 32 bytes of entropy (from the system source, such as /dev/random) are automatically added to seed the PRNG.
Returns TRUE for success, FALSE for failure.
topGetEntropy
const char *CkPrng_getEntropy(HCkPrng cHandle, int numBytes, const char *encoding);
Reads real entropy bytes from a system entropy source and returns as an encoded string. On Linux/Unix based systems, including MAC OS X, this is accomplished by reading /dev/random. On Windows systems, it uses the Microsoft Cryptographic Service Provider's CryptGenRandom method.
It is recommended that no more than 32 bytes of entropy should be retrieved to initially seed a PRNG. Larger amounts of entropy are fairly useless. However, an app is free to periodically add bits of entropy to a long-running PRNG as it sees fit.
The encoding specifies the encoding to be used. It can be "hex", "base64", or many other possibilities. See the link below.
Returns TRUE for success, FALSE for failure.
GetEntropyBytes
Reads and returns real entropy bytes from a system entropy source. On Linux/Unix based systems, including MAC OS X, this is accomplished by reading /dev/random. On Windows systems, it uses the Microsoft Cryptographic Service Provider's CryptGenRandom method.
It is recommended that no more than 32 bytes of entropy should be retrieved to initially seed a PRNG. Larger amounts of entropy are fairly useless. However, an app is free to periodically add bits of entropy to a long-running PRNG as it sees fit.
Returns TRUE for success, FALSE for failure.
topImportEntropy
Imports entropy from previously exported entropy. See the ExportEntropy method for more information.
Returns TRUE for success, FALSE for failure.
RandomInt
Generates and returns a random integer between low and high (inclusive). For example, if low is 4 and high is 8, then random integers in the range 4, 5, 6, 7, 8 are returned.
RandomPassword
const char *CkPrng_randomPassword(HCkPrng cHandle, int length, BOOL mustIncludeDigit, BOOL upperAndLowercase, const char *mustHaveOneOf, const char *excludeChars);
Generates and returns a random password of a specified length. If mustIncludeDigit is TRUE, the generated password will contain at least one digit (0-9). If upperAndLowercase is TRUE, then generated password will contain both lowercase and uppercase USASCII chars (a-z and A-Z). If mustHaveOneOf is a non-empty string, it contains the set of non-alphanumeric characters, one of which must be included in the password. For example, mustHaveOneOf might be the string "!@#$%". If excludeChars is a non-empty string, it contains chars that should be excluded from the password. A typical need would be to exclude chars that appear similar to others, such as i, l, 1, L, o, 0, O.
Returns TRUE for success, FALSE for failure.
RandomString
const char *CkPrng_randomString(HCkPrng cHandle, int length, BOOL bDigits, BOOL bLower, BOOL bUpper);
Generates and returns a random string that may contain digits (0-9), lowercase ASCII (a-z) , and uppercase ASCII (A-Z). To include numeric digits, set bDigits equal to TRUE. To include lowercase ASCII, set bLower equal to TRUE. To include uppercase ASCII, set bUpper equal to TRUE. The length of the string to be generated is specified by length.
Returns TRUE for success, FALSE for failure.