implementing-rsa-key-pair-management

Implementing RSA Key Pair Management

Overview

RSA (Rivest-Shamir-Adleman) is the most widely deployed asymmetric cryptographic algorithm, used for digital signatures, key exchange, and encryption. This skill covers generating, storing, rotating, and managing RSA key pairs following NIST SP 800-57 key management guidelines, including key serialization formats (PEM, DER, PKCS#8), passphrase protection, and key strength validation.

When to Use

• When deploying or configuring implementing rsa key pair management capabilities in your environment
• When establishing security controls aligned to compliance requirements
• When building or improving security architecture for this domain
• When conducting security assessments that require this implementation

Prerequisites

• Familiarity with cryptography concepts and tools
• Access to a test or lab environment for safe execution
• Python 3.8+ with required dependencies installed
• Appropriate authorization for any testing activities

Objectives

• Generate RSA key pairs with appropriate key sizes (2048, 3072, 4096 bits)
• Serialize keys in PEM and DER formats with PKCS#8
• Protect private keys with strong passphrase encryption
• Implement key rotation with versioning
• Extract public key components and fingerprints
• Validate key strength and detect weak keys
• Sign and verify data using RSA-PSS

Key Concepts

RSA Key Sizes and Security Strength

| Key Size (bits) | Security Strength (bits) | Recommended Until |

|-----------------|-------------------------|-------------------|

| 2048 | 112 | 2030 |

| 3072 | 128 | Beyond 2030 |

| 4096 | ~140 | Beyond 2030 |

RSA Padding Schemes

| Scheme | Use Case | Standard |

|--------|----------|----------|

| OAEP | Encryption | PKCS#1 v2.2 (RFC 8017) |

| PSS | Signatures | PKCS#1 v2.2 (RFC 8017) |

| PKCS#1 v1.5 | Legacy only | Deprecated for new systems |

Key Storage Formats

• PEM: Base64-encoded with headers, human-readable
• DER: Binary ASN.1 encoding, compact
• PKCS#8: Standard for private key encapsulation
• PKCS#12/PFX: Bundled key + certificate, password-protected

Security Considerations

• Minimum 3072-bit keys for new deployments (NIST recommendation)
• Always protect private keys with AES-256-CBC passphrase encryption
• Use RSA-PSS for signatures (not PKCS#1 v1.5)
• Use RSA-OAEP for encryption (not PKCS#1 v1.5)
• Store private keys with restrictive file permissions (0600)
• Implement key rotation at least annually

Validation Criteria

• [ ] Key generation produces valid RSA key pair
• [ ] Public key can be extracted from private key
• [ ] Private key is protected with passphrase
• [ ] RSA-PSS signature verification succeeds
• [ ] Tampered signature verification fails
• [ ] Key fingerprint is computed correctly
• [ ] Key rotation maintains old key access for verification