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name: implementing-rsa-key-pair-management description: 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, domain: cybersecurity subdomain: cryptography tags: [cryptography, rsa, key-management, pki, asymmetric-encryption] version: "1.0" author: mahipal license: Apache-2.0

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.

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