====== Classic -> Hybrid Migration ======

<WRAP round info>
**Complexity:** Medium \\
**Duration:** 6-12 months (complete) \\
**Risk:** Low-Medium
</WRAP>

Gradual migration from classic PKI (RSA/ECDSA) to hybrid mode (Classic + ML-DSA).

----

===== Overview =====

<mermaid>
flowchart TB
    subgraph PHASE1["Phase 1: Preparation"]
        P1A[Inventory]
        P1B[Test environment]
        P1C[Tooling update]
    end

    subgraph PHASE2["Phase 2: Infrastructure"]
        P2A[Root CA Hybrid]
        P2B[Intermediate CAs]
        P2C[CRL/OCSP update]
    end

    subgraph PHASE3["Phase 3: Rollout"]
        P3A[Server certificates]
        P3B[Client certificates]
        P3C[Code signing]
    end

    subgraph PHASE4["Phase 4: Validation"]
        P4A[Monitoring]
        P4B[Audit]
        P4C[Documentation]
    end

    P1A --> P1B --> P1C --> P2A
    P2A --> P2B --> P2C --> P3A
    P3A --> P3B --> P3C --> P4A
    P4A --> P4B --> P4C

    style P2A fill:#fff3e0
    style P3A fill:#e8f5e9
</mermaid>

----

===== Phase 1: Preparation (1-2 months) =====

==== 1.1 Perform Inventory ====

<code bash>
#!/bin/bash
# inventory-certs.sh - Certificate inventory

echo "=== Certificate Inventory $(date) ===" > inventory.csv
echo "Path,Subject,Algorithm,KeySize,Expiry,Days" >> inventory.csv

# Local certificates
for cert in /etc/ssl/certs/*.pem /etc/pki/tls/certs/*.pem; do
    [ -f "$cert" ] || continue

    subject=$(openssl x509 -in "$cert" -subject -noout 2>/dev/null | sed 's/subject=//')
    algo=$(openssl x509 -in "$cert" -text -noout 2>/dev/null | grep "Public Key Algorithm" | awk '{print $4}')
    keysize=$(openssl x509 -in "$cert" -text -noout 2>/dev/null | grep "Public-Key:" | grep -oP '\d+')
    expiry=$(openssl x509 -in "$cert" -enddate -noout 2>/dev/null | cut -d= -f2)
    days=$(( ($(date -d "$expiry" +%s) - $(date +%s)) / 86400 ))

    echo "\"$cert\",\"$subject\",\"$algo\",\"$keysize\",\"$expiry\",\"$days\"" >> inventory.csv
done

# Remote endpoints
ENDPOINTS=(
    "api.example.com:443"
    "web.example.com:443"
    "mail.example.com:465"
)

for endpoint in "${ENDPOINTS[@]}"; do
    host=${endpoint%:*}
    port=${endpoint#*:}

    cert_info=$(echo | openssl s_client -connect "$endpoint" -servername "$host" 2>/dev/null | openssl x509 -text -noout 2>/dev/null)
    # ... evaluate analogously
done

echo "Inventory completed: inventory.csv"
</code>

-> Details: [[.:inventur|Certificate Inventory]]

==== 1.2 Set Up Test Environment ====

<code bash>
# Docker-based test PKI
docker run -d --name test-ca \
    -v /test-pki:/pki \
    -e OPENSSL_CONF=/pki/openssl.cnf \
    alpine/openssl

# OpenSSL 3.6 for PQ
docker exec test-ca openssl version
# OpenSSL 3.6.0 ...

# Test: Create hybrid certificate
docker exec test-ca openssl genpkey -algorithm ML-DSA-65 -out /pki/test-mldsa.key
</code>

==== 1.3 Tooling Update ====

| Tool | Min. Version | PQ Support |
|------|--------------|------------|
| OpenSSL | 3.6.0 | ML-DSA, ML-KEM |
| .NET | 9.0+ | Via WvdS.System.Security.Cryptography |
| Java | 21+ | Via BouncyCastle 1.78 |
| curl | 8.5+ | Hybrid TLS |

----

===== Phase 2: Infrastructure (2-3 months) =====

==== 2.1 Migrate Root CA to Hybrid ====

<WRAP round important>
**Root CA migration is the most critical step.** Plan carefully and test extensively.
</WRAP>

**Option A: New Hybrid Root CA (recommended)**

<code csharp>
// Create new hybrid Root CA
using var ecdsa = ECDsa.Create(ECCurve.NamedCurves.nistP384);
var request = new CertificateRequest(
    "CN=My Organization Root CA - Hybrid, O=My Organization",
    ecdsa,
    HashAlgorithmName.SHA384);

// CA Extensions
request.CertificateExtensions.Add(
    new X509BasicConstraintsExtension(true, true, 2, true));
request.CertificateExtensions.Add(
    new X509KeyUsageExtension(
        X509KeyUsageFlags.KeyCertSign | X509KeyUsageFlags.CrlSign,
        true));

// Hybrid self-signed (ECDSA + ML-DSA)
var hybridRoot = request.CreateSelfSigned(
    DateTimeOffset.UtcNow,
    DateTimeOffset.UtcNow.AddYears(25),
    CryptoMode.Hybrid);

// Export
File.WriteAllBytes("hybrid-root-ca.pfx",
    hybridRoot.Export(X509ContentType.Pfx, "secure-password"));
</code>

**Option B: Cross-Certification (Transition)**

<code csharp>
// Old Root CA cross-certifies new hybrid CA
using var oldRoot = new X509Certificate2("old-root.pfx", "password");
using var newHybridRoot = new X509Certificate2("hybrid-root.pfx", "password");

// Create cross certificate
var crossCertRequest = new CertificateRequest(
    newHybridRoot.SubjectName,
    newHybridRoot.GetECDsaPublicKey()!,
    HashAlgorithmName.SHA384);

// Signed by old root
var crossCert = crossCertRequest.Create(
    oldRoot,
    newHybridRoot.NotBefore,
    newHybridRoot.NotAfter,
    newHybridRoot.SerialNumberBytes.ToArray());
</code>

==== 2.2 Migrate Intermediate CAs ====

<code bash>
# New hybrid intermediate CA
# 1. Generate key
openssl genpkey -algorithm EC -pkeyopt ec_paramgen_curve:P-384 -out intermediate.key

# 2. Create CSR
openssl req -new -key intermediate.key \
    -out intermediate.csr \
    -subj "/CN=My Organization Intermediate CA - Hybrid/O=My Organization"

# 3. Sign with hybrid root (with WvdS)
</code>

<code csharp>
// Sign intermediate with hybrid root
using var hybridRoot = new X509Certificate2("hybrid-root.pfx", "password");

var intermediateCsr = CertificateRequest.LoadSigningRequest(
    File.ReadAllBytes("intermediate.csr"),
    HashAlgorithmName.SHA384);

// Add CA extensions
intermediateCsr.CertificateExtensions.Add(
    new X509BasicConstraintsExtension(true, true, 1, true));

var intermediate = intermediateCsr.Create(
    hybridRoot,
    DateTimeOffset.UtcNow,
    DateTimeOffset.UtcNow.AddYears(10),
    Guid.NewGuid().ToByteArray(),
    CryptoMode.Hybrid);
</code>

==== 2.3 CRL/OCSP Update ====

<code csharp>
// Create hybrid-signed CRL
var crlBuilder = new CertificateRevocationListBuilder();

// Transfer old CRL entries
foreach (var entry in existingCrlEntries)
{
    crlBuilder.AddEntry(entry.SerialNumber, entry.RevocationDate, entry.Reason);
}

// Sign with hybrid CA
byte[] newCrl = crlBuilder.Build(
    hybridIntermediate,
    newCrlNumber,
    DateTimeOffset.UtcNow.AddDays(7),
    HashAlgorithmName.SHA384,
    CryptoMode.Hybrid);
</code>

----

===== Phase 3: Rollout (3-6 months) =====

==== 3.1 Server Certificates ====

**Priority Matrix:**

| Server Type | Priority | Reason |
|-------------|----------|--------|
| External-facing API | High | Highest risk |
| Internal microservices | Medium | Lateral movement |
| Development | Low | Test environment |

<code bash>
# Batch renewal with hybrid
for server in $(cat servers.txt); do
    # Create CSR
    ssh "$server" "openssl req -new -key /etc/ssl/private/server.key \
        -out /tmp/renew.csr -subj \"/CN=$server\""

    # Fetch CSR
    scp "$server:/tmp/renew.csr" "./csrs/$server.csr"

    # Issue hybrid certificate (via API or script)
    ./sign-hybrid.sh "./csrs/$server.csr" "./certs/$server.pem"

    # Deploy certificate
    scp "./certs/$server.pem" "$server:/etc/ssl/certs/server.pem"
    ssh "$server" "systemctl reload nginx"
done
</code>

==== 3.2 Client Certificates ====

<code csharp>
// Issue client certificate with hybrid
var clientCsr = CertificateRequest.LoadSigningRequest(csrBytes, HashAlgorithmName.SHA384);

clientCsr.CertificateExtensions.Add(
    new X509EnhancedKeyUsageExtension(
        new OidCollection { new Oid("1.3.6.1.5.5.7.3.2") }, // Client Auth
        false));

var clientCert = clientCsr.Create(
    intermediate,
    DateTimeOffset.UtcNow,
    DateTimeOffset.UtcNow.AddYears(1),
    Guid.NewGuid().ToByteArray(),
    CryptoMode.Hybrid);
</code>

==== 3.3 Code Signing Certificates ====

-> See [[..:automatisierung:cicd-code-signing|CI/CD Code Signing]] for pipeline integration

----

===== Phase 4: Validation (1-2 months) =====

==== 4.1 Enable Monitoring ====

<code yaml>
# Prometheus alert for hybrid status
- alert: NonHybridCertificateInProduction
  expr: x509_cert_algorithm{env="production"} !~ ".*ML-DSA.*|.*Hybrid.*"
  for: 24h
  labels:
    severity: warning
  annotations:
    summary: "Non-hybrid certificate in production: {{ $labels.filepath }}"
</code>

==== 4.2 Checklist ====

| # | Checkpoint | Status |
|---|------------|--------|
| 1 | All CA certificates on hybrid | |
| 2 | All server certificates renewed | |
| 3 | CRL/OCSP signed with hybrid | |
| 4 | Trust stores updated | |
| 5 | Monitoring shows no classic-only | |
| 6 | Rollback tested | |
| 7 | Documentation updated | |

----

===== Rollback Plan =====

<WRAP round alert>
**On problems:**
</WRAP>

<code bash>
# 1. Switch back to classic CA
export CA_CERT=/etc/pki/CA/classic-intermediate.pem
export CA_KEY=/etc/pki/CA/classic-intermediate.key

# 2. Reissue certificates with classic CA
./issue-classic.sh

# 3. Revoke hybrid CA certificates (if needed)
./revoke-hybrid-certs.sh
</code>

-> Details: [[.:rollback-strategie|Rollback Strategy]]

----

===== Related Documentation =====

  * [[.:parallel-betrieb|Parallel Operation]] - Alternative strategy
  * [[.:inventur|Inventory]] - Detailed inventory
  * [[en:int:pqcrypt:konzepte:start|Crypto Modes]] - Hybrid explained

----

<< [[.:start|<- Migration]] | [[.:parallel-betrieb|-> Parallel Operation]] >>

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

{{tag>migration hybrid classic upgrade operator}}