How to Generate Secure Random Integers and Tokens Using 'crypto/rand'?

Random Int Generation using "crypto/rand.Int"

Within the "crypto/rand" package lies the necessity to generate secure random integers. An example of how to achieve this between the range of 0 to 27 is below:

package main

import (
    "crypto/rand"
    "fmt"
    "math/big"
)

func main() {
    nBig, err := rand.Int(rand.Reader, big.NewInt(27))
    if err != nil {
        panic(err)
    }
    n := nBig.Int64()
    fmt.Printf("Random int in [0,27): %d\n", n)
}

This function utilizes the "rand.Reader" and the "big.Int" type from "math/big" library to achieve cryptographic randomness beyond the int range.

Secure Token Generation

However, in the context of generating secure tokens, an alternative and more appropriate approach is recommended:

package main

import (
    "crypto/rand"
    "encoding/base32"
    "fmt"
)

func main() {
    token := getToken(10)
    fmt.Printf("Secure token: %s\n", token)
}

func getToken(length int) string {
    randomBytes := make([]byte, 32)
    _, err := rand.Read(randomBytes)
    if err != nil {
        panic(err)
    }
    return base32.StdEncoding.EncodeToString(randomBytes)[:length]
}

In this scenario, random bytes are generated, then encoded using "base32" to create a token. This approach is deemed sufficient for secure token generation.

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