Package com.chilkatsoft.chilkat2

Class Prng

java.lang.Object
com.chilkatsoft.chilkat2.ChilkatObject
com.chilkatsoft.chilkat2.Prng
All Implemented Interfaces:
AutoCloseable
public class Prng extends ChilkatObject
<section class="prng-summary">

Generate random bytes, encoded values, passwords, and application identifiers.

Use Chilkat.Prng when an application needs random bytes or random text values for cryptographic or application-level purposes. The class can seed itself automatically from the system entropy source, accept additional entropy from the application, and produce random data as raw bytes, encoded strings, passwords, integers, booleans, GUID-style values, or higher-level identifiers such as Firebase Push IDs.

Random bytes

Generate random byte data for keys, IVs, nonces, salts, tokens, test data, or protocol-specific binary values.

Encoded random strings

Produce random values encoded as Base64, hex, URL-safe text, or other supported encodings when binary data must be represented as text.

Password generation

Create random passwords using configurable character sets and length requirements.

Entropy input

Allow the PRNG to seed from the system entropy source and optionally add application-provided entropy.

Random application values

Generate random integers, booleans, GUID-style values, and other convenient random outputs for application logic.

Firebase Push IDs

Create Firebase-style push IDs for applications that need sortable, client-generated identifiers.

Common pattern: Use Prng to create random material in the form required by the caller: bytes for cryptographic inputs, encoded strings for tokens or API values, passwords for user-facing credentials, or Firebase Push IDs for sortable identifiers. For cryptographic workflows, generate enough random bytes for the algorithm or protocol and avoid reducing randomness by truncating or reformatting values incorrectly.

For an extended overview, see Prng Class Overview.

</section>

Instances hold a native Chilkat object: close them with ChilkatObject.close() (try-with-resources) when done; an unclosed instance is freed when it becomes unreachable.

See Also:
Online reference

  • Constructor Details

    • Prng

      public Prng()
      Creates a new Prng object.

  • Method Details

    • getPrngName

      public String getPrngName()
      Selects the pseudo-random number generator used by this object. The only supported value is fortuna, which is also the default. Chilkat's Fortuna implementation uses AES-256 for generation and SHA-256 in its entropy-processing and reseeding design.

      Compatibility note: Assigning any value other than fortuna is ignored. Applications should normally leave this property unchanged.

      Returns:
      the value of the PrngName property

    • setPrngName

      public void setPrngName​(String value)
      Sets the PrngName property; see getPrngName().
      Parameters:
      value - the new value (not null)

    • addEntropy

      public void addEntropy​(String entropy, String encoding)
      Adds caller-supplied seed material to the PRNG. entropy contains the bytes in the text encoding named by encoding, such as hex, base64, or ascii. For Fortuna, the decoded bytes are incorporated into the internal entropy pools and become available to later reseeding.

      This method is optional and is not the normal way an application obtains entropy for the PRNG. It may be called more than once and at any point during the lifetime of the object. It returns true when the input is decoded and accepted, or false if the encoding is invalid or another error occurs.

      Automatic system seeding: If no entropy has been added before the first request for random output, Chilkat automatically obtains 32 bytes from the platform's cryptographic system entropy source to seed the PRNG. This is the normal and recommended mode of operation. Call AddEntropy only when the application has additional trustworthy entropy to contribute or deliberately needs deterministic seeding for testing.Repeatable tests: A fresh Prng object can be seeded with the same deterministic values to reproduce the same output sequence, provided the same entropy calls and random-generation calls occur in the same order. Predictable seed material is appropriate only for tests and debugging. Do not use it for real keys, nonces, passwords, or tokens.

      Parameters:
      entropy - the entropy argument (not null)
      encoding - the encoding argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • exportEntropy

      public String exportEntropy()
      Exports a Base64-encoded value derived from the PRNG's accumulated entropy pools. The internal pools are rehashed for export so the returned value is not a direct disclosure of the generator state.

      The returned value can be persisted and supplied to ImportEntropy when a later process starts. For language bindings in which this method directly returns a string, check LastMethodSuccess before using the result.

      Seed-file guidance: Imported entropy can improve startup behavior, but it should not be the only seed used indefinitely. After importing, also allow Chilkat to obtain fresh operating-system entropy. Protect persisted entropy from unauthorized modification and accidental reuse across cloned systems.

      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • firebasePushId

      public String firebasePushId()
      Generates a Firebase-compatible push ID. A push ID is a 20-character identifier built from a 48-bit millisecond timestamp followed by 72 bits of randomness, encoded with Firebase's ordered 64-character alphabet.

      The timestamp prefix makes push IDs sort approximately by creation time, while the random portion makes collisions highly unlikely across independent clients. For language bindings in which this method directly returns a string, check LastMethodSuccess before using the result.

      Not a secret: A push ID is an identifier, not an authentication token. Its prefix reveals approximate creation time, and uniqueness is probabilistic rather than an absolute guarantee.

      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genRandom

      public String genRandom​(int numBytes, String encoding)
      Generates numBytes random bytes and returns those bytes as text using the encoding named by encoding, such as hex, base64, or base64url. numBytes is the number of binary bytes before text encoding; it is not the number of output characters.

      If no entropy has been added before the first request for random output, Chilkat automatically obtains 32 bytes from the platform's cryptographic system entropy source to seed the PRNG.

      For language bindings in which this method directly returns a string, check LastMethodSuccess before using the result.

      Encoding does not add entropy: Hex, Base64, and other encodings represent the same random bytes in different textual forms. Choose numBytes from the security requirement of the key, nonce, salt, or token—not from the desired text length.

      Parameters:
      numBytes - the numBytes argument
      encoding - the encoding argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • genRandomBd

      public void genRandomBd​(int numBytes, BinData bd)
      Generates numBytes random bytes and appends them to the existing contents of the BinData object passed in bd. The destination is not cleared before the bytes are added.

      If no entropy has been added before the first request for random output, Chilkat automatically obtains 32 bytes from the platform's cryptographic system entropy source to seed the PRNG.

      Returns true on success or false on failure.

      Appending behavior: Call BinData.Clear first when the destination should contain only the newly generated bytes.

      Parameters:
      numBytes - the numBytes argument
      bd - the bd argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • getEntropy

      public String getEntropy​(int numBytes, String encoding)
      Requests numBytes bytes from the platform's cryptographic system entropy source and returns them using the text encoding named by encoding. This obtains system-provided random seed material directly; it is different from asking the Fortuna generator to expand its current state with GenRandom.

      For seeding this PRNG, 32 bytes normally provide the full 256-bit seed input expected by the implementation. Applications may request another amount when a protocol specifically requires raw bytes from the system source.

      For language bindings in which this method directly returns a string, check LastMethodSuccess before using the result.

      Usually unnecessary: The simplest secure use is to call a random-generation method directly. If no entropy was added explicitly, Chilkat automatically obtains 32 bytes of system entropy on the first generation request.

      Parameters:
      numBytes - the numBytes argument
      encoding - the encoding argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • importEntropy

      public void importEntropy​(String entropy)
      Imports the Base64-encoded entropy value previously returned by ExportEntropy. The imported material is supplied to the PRNG for use in its entropy and reseeding process.

      Returns true if the value is valid and imported successfully. Returns false if it cannot be decoded or imported; check LastErrorText for details.

      Recommended startup sequence: Import persisted entropy before the first random-generation call, then mix in fresh system entropy or allow the first generation call to perform Chilkat's automatic system seeding.

      Parameters:
      entropy - the entropy argument (not null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • randomInt

      public int randomInt​(int low, int high)
      Returns a pseudorandom integer in the inclusive range from low through high. For example, RandomInt(4, 8) can return 4, 5, 6, 7, or 8.

      The caller should ensure that low is less than or equal to high.

      Cryptographic material: Use GenRandom, GenRandomBytes, or GenRandomBd when a protocol requires an exact number of random bytes. Do not assemble keys or nonces from decimal random integers unless the protocol explicitly defines that representation.

      Parameters:
      low - the low argument
      high - the high argument
      Returns:
      the result (see ChilkatObject.getLastMethodSuccess() where the description mentions failure)

    • randomPassword

      public String randomPassword​(int length, boolean mustIncludeDigit, boolean upperAndLowercase, String mustHaveOneOf, String excludeChars)
      Generates a password of exactly length characters while applying the requested composition rules:

      Argument Effect

      mustIncludeDigit When true, require at least one digit from 0-9.

      upperAndLowercase When true, require at least one lowercase and at least one uppercase US-ASCII letter.

      mustHaveOneOf When nonempty, require at least one character from this supplied set, such as !@#$%.

      excludeChars Exclude every listed character from the generated password. This is useful for ambiguous characters such as iIlL1oO0.

      The requested length must be large enough to satisfy all enabled requirements, and exclusions must not remove every usable character from a required category. For language bindings in which this method directly returns a string, check LastMethodSuccess before using the result.

      Password policy note: Longer randomly generated passwords generally provide more security than short passwords with many composition rules. Also ensure the receiving system accepts every character that may be generated.

      Parameters:
      length - the length argument
      mustIncludeDigit - the mustIncludeDigit argument
      upperAndLowercase - the upperAndLowercase argument
      mustHaveOneOf - the mustHaveOneOf argument (not null)
      excludeChars - the excludeChars argument (not null)
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why

    • randomString

      public String randomString​(int length, boolean bDigits, boolean bLower, boolean bUpper)
      Generates a string of exactly length characters. The remaining arguments select the character categories placed in the source alphabet:

      Argument When true

      bDigits Include digits 0-9.

      bLower Include lowercase ASCII letters a-z.

      bUpper Include uppercase ASCII letters A-Z.

      At least one character category must be enabled. The flags define the pool from which each character is chosen; they do not guarantee that every enabled category appears in a particular result.

      Requirement-aware passwords: Use RandomPassword instead when the result must contain at least one digit, both uppercase and lowercase letters, or a required special character.

      Parameters:
      length - the length argument
      bDigits - the bDigits argument
      bLower - the bLower argument
      bUpper - the bUpper argument
      Returns:
      the result (never null)
      Throws:
      ChilkatException - if the operation fails; ChilkatException.getLastErrorText() says why