iOS Certificate Trust Behavior

1 min read SSL/TLS & Certificates

iOS Certificate Trust Behavior

iOS maintains strict certificate validation with limited user override options. Safari blocks access to sites with certificate errors, providing minimal technical details. iOS requires complete certificate chains and rejects certificates with weak signatures or outdated algorithms.

iOS-specific considerations:

# Requirements for iOS compatibility
# - Complete certificate chain
# - SHA-256 signature minimum
# - RSA 2048-bit or ECC 256-bit keys
# - Valid certificate transparency logs

# Test iOS compatibility
openssl s_client -connect example.com:443 -servername example.com < /dev/null 2>/dev/null | openssl x509 -text -noout | grep -E "Signature Algorithm|Public-Key"

Install custom CA certificates on iOS:

  1. Email certificate file to device
  2. Open attachment and select "Install"
  3. Navigate to Settings → General → Profiles
  4. Tap certificate profile and install
  5. Enable trust in Settings → General → About → Certificate Trust Settings