~~NOTOC~~
====== Scenario 4.3: Certificate Archival ======

<WRAP round info>
**Category:** [[.:start|Certificate Management]] \\
**Complexity:** ⭐⭐⭐ (Medium) \\
**Prerequisites:** Expired/revoked certificates \\
**Estimated Time:** 15-20 Minutes
</WRAP>

----

===== Description =====

This scenario describes the **secure archival** of certificates and associated keys. Archival is necessary for:

  * **Compliance retention requirements** (GDPR, NIS2)
  * **Forensic traceability**
  * **Decryption of historical data**
  * **Audit evidence**

<WRAP round important>
**Important:** Encryption keys must be archived if encrypted data still exists. Signature keys should NOT be archived (only certificates).
</WRAP>

----

===== Workflow =====

<mermaid>
flowchart TD
    CERT[Certificate Expired/Revoked] --> CLASSIFY{Key Type?}
    CLASSIFY -->|Encryption| ARCHIVE_KEY[Archive Key]
    CLASSIFY -->|Signature| DESTROY_KEY[Destroy Key]
    ARCHIVE_KEY --> ENCRYPT[Store Encrypted]
    DESTROY_KEY --> ARCHIVE_CERT[Archive Certificate Only]
    ENCRYPT --> STORE[Archive Storage]
    ARCHIVE_CERT --> STORE
    STORE --> LOG[Audit Log]

    style ENCRYPT fill:#fff3e0
    style STORE fill:#e8f5e9
</mermaid>

----

===== Code Example (C#) =====

<code csharp>
using WvdS.Security.Cryptography.X509Certificates.Extensions.PQ;

using var ctx = PqCryptoContext.Initialize();

// Load certificates to archive
var expiredCert = ctx.LoadCertificate("old-server.crt.pem");
var expiredKey = ctx.LoadPrivateKey("old-server.key.pem", "OldPassword!");

// Archive structure
var archive = new CertificateArchive
{
    Certificate = expiredCert,
    ArchivedAt = DateTime.UtcNow,
    OriginalPath = "old-server.crt.pem",
    Reason = ArchiveReason.Expired,
    RetentionUntil = DateTime.UtcNow.AddYears(10),
    Metadata = new Dictionary<string, string>
    {
        ["Subject"] = expiredCert.Subject,
        ["SerialNumber"] = expiredCert.SerialNumber,
        ["NotBefore"] = expiredCert.NotBefore.ToString("O"),
        ["NotAfter"] = expiredCert.NotAfter.ToString("O"),
        ["Thumbprint"] = expiredCert.Thumbprint,
        ["KeyUsage"] = GetKeyUsageString(expiredCert)
    }
};

// Archive key only for encryption certificates
if (HasKeyEncipherment(expiredCert))
{
    // Store key encrypted
    var encryptedKey = ctx.EncryptPrivateKey(
        expiredKey,
        archivePassword: "ArchivePassword!SecureVault2024",
        algorithm: PbeAlgorithm.Aes256Cbc,
        prf: PbePrf.HmacSha256,
        iterations: 100000
    );
    archive.EncryptedPrivateKey = encryptedKey;
}

// Archive as JSON
var archivePath = $"archive/{expiredCert.SerialNumber}.json";
File.WriteAllText(archivePath, JsonSerializer.Serialize(archive, new JsonSerializerOptions
{
    WriteIndented = true
}));

// Audit log
Console.WriteLine($"Archived: {expiredCert.Subject}");
Console.WriteLine($"  Serial: {expiredCert.SerialNumber}");
Console.WriteLine($"  Expiry: {expiredCert.NotAfter:yyyy-MM-dd}");
Console.WriteLine($"  Archive: {archivePath}");
Console.WriteLine($"  Retention until: {archive.RetentionUntil:yyyy-MM-dd}");
</code>

----

===== Archive Data Structure =====

<code csharp>
public class CertificateArchive
{
    public string Version { get; } = "1.0";
    public DateTime ArchivedAt { get; set; }
    public X509Certificate2 Certificate { get; set; }
    public byte[]? EncryptedPrivateKey { get; set; }  // Only for encryption certs
    public string OriginalPath { get; set; }
    public ArchiveReason Reason { get; set; }
    public DateTime RetentionUntil { get; set; }
    public Dictionary<string, string> Metadata { get; set; }
    public string? Notes { get; set; }
}

public enum ArchiveReason
{
    Expired,
    Revoked,
    Superseded,
    KeyCompromise,
    CessationOfOperation,
    PolicyChange
}
</code>

----

===== Industry-Specific Retention Periods =====

^  Industry  ^  Regulation  ^  Retention Period  ^  Archive Keys?  ^
| **Financial Sector** | SOX, PCI | 10 years | Yes (encryption) |
| **Healthcare** | GDPR, HIPAA | 30 years | Yes (patient data) |
| **Energy** | NIS2 | 10 years | Yes (metering data) |
| **Public Sector** | Archive laws | 30+ years | Depending on data type |
| **Standard IT** | GDPR | 6 years | No (certificate only) |

----

===== Create Archive Directory =====

<code csharp>
// Structured archive directory
public class ArchiveDirectory
{
    private readonly string _basePath;

    public ArchiveDirectory(string basePath)
    {
        _basePath = basePath;
        Directory.CreateDirectory(Path.Combine(basePath, "certificates"));
        Directory.CreateDirectory(Path.Combine(basePath, "keys"));
        Directory.CreateDirectory(Path.Combine(basePath, "metadata"));
    }

    public void Archive(CertificateArchive archive)
    {
        var serial = archive.Certificate.SerialNumber;
        var year = archive.Certificate.NotAfter.Year;

        // Certificate (PEM)
        var certPath = Path.Combine(_basePath, "certificates", $"{year}", $"{serial}.crt.pem");
        Directory.CreateDirectory(Path.GetDirectoryName(certPath)!);
        archive.Certificate.ToPemFile(certPath);

        // Key (if present)
        if (archive.EncryptedPrivateKey != null)
        {
            var keyPath = Path.Combine(_basePath, "keys", $"{year}", $"{serial}.key.enc");
            Directory.CreateDirectory(Path.GetDirectoryName(keyPath)!);
            File.WriteAllBytes(keyPath, archive.EncryptedPrivateKey);
        }

        // Metadata
        var metaPath = Path.Combine(_basePath, "metadata", $"{year}", $"{serial}.json");
        Directory.CreateDirectory(Path.GetDirectoryName(metaPath)!);
        File.WriteAllText(metaPath, JsonSerializer.Serialize(archive.Metadata));
    }
}
</code>

----

===== Archive Search =====

<code csharp>
// Search archived certificates
public IEnumerable<CertificateArchive> SearchArchive(
    string basePath,
    string? subjectFilter = null,
    DateTime? expiredAfter = null)
{
    var metadataFiles = Directory.GetFiles(
        Path.Combine(basePath, "metadata"),
        "*.json",
        SearchOption.AllDirectories
    );

    foreach (var file in metadataFiles)
    {
        var metadata = JsonSerializer.Deserialize<Dictionary<string, string>>(
            File.ReadAllText(file)
        );

        if (subjectFilter != null &&
            !metadata["Subject"].Contains(subjectFilter, StringComparison.OrdinalIgnoreCase))
            continue;

        if (expiredAfter.HasValue &&
            DateTime.Parse(metadata["NotAfter"]) < expiredAfter.Value)
            continue;

        var serial = Path.GetFileNameWithoutExtension(file);
        var year = Path.GetFileName(Path.GetDirectoryName(file));

        yield return LoadArchive(basePath, year, serial);
    }
}
</code>

----

===== Related Scenarios =====

^  Relationship  ^  Scenario  ^  Description  ^
| **Prerequisite** | [[.:backup|4.4 Backup]] | Backup before archival |
| **Related** | [[en:int:pqcrypt:szenarien:schluessel:vernichtung|11.5 Key Destruction]] | Delete signature keys |
| **Related** | [[en:int:pqcrypt:szenarien:widerruf:zertifikat_widerrufen|6.4 Revoke]] | Before archival |

----

<< [[.:rekey|← 4.2 Rekey]] | [[.:start|↑ Management Overview]] | [[.:backup|4.4 Backup →]] >>

{{tag>scenario management archival compliance retention}}

----
//Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional//