Argon2 Hash (Argon2i, Argon2d, Argon2id) Regex for Go

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching argon2 hash (argon2i, argon2d, argon2id), ported and verified for Go. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// Argon2 Hash (Argon2i, Argon2d, Argon2id)
// ReDoS-safe | RegexVault — Security > Password Formats

package validation

import "regexp"

var argon2HashArgon2iArgon2dArgon2idRe = regexp.MustCompile(`^\$(argon2(?:i|d|id))\$v=19\$m=([0-9]+),t=([0-9]+),p=([0-9]+)(?:,keyid=[A-Za-z0-9+/]{0,11}(?:=*))?(?:,data=[A-Za-z0-9+/]{0,43}(?:=*))?\$([A-Za-z0-9+/]{11,64}(?:={0,2}))\$([A-Za-z0-9+/]{16,86}(?:={0,2}))$`)

func ValidateArgon2HashArgon2iArgon2dArgon2id(s string) bool {
    return argon2HashArgon2iArgon2dArgon2idRe.MatchString(s)
}

// Example
// fmt.Println(ValidateArgon2HashArgon2iArgon2dArgon2id("$argon2id$v=19$m=65536,t=2,p=1$c29tZXNhbHQ$RdescudvJCsgt3ub+b+dWRWJTmaaJObG")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats category and carries a ReDoS-safe certification. That matters for Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Argon2id is the recommended variant (memory-hard + side-channel resistant). Parameters: m=memory in KiB, t=time iterations, p=parallelism. OWASP recommends argon2id with m=19456 (19 MiB), t=2, p=1 as minimum. v=19 is the current version.