Crypto Operations
Advanced Encryption Standard - symmetric encryption algorithm
AES Encrypt
Encrypt text using AES-256-CBC algorithm
AES Decrypt
Decrypt AES encrypted text
Input
Output
Cryptographic Algorithms Detailed Introduction
AES (Advanced Encryption Standard)
Algorithm Overview
AES is a symmetric encryption standard established by the National Institute of Standards and Technology (NIST) in 2001, and is one of the most widely used encryption algorithms in the world today. It uses a block cipher system with the same key for both encryption and decryption operations.
Technical Characteristics
- • Key Length: Supports three key lengths: 128-bit, 192-bit, and 256-bit
- • Block Size: Fixed at 128 bits (16 bytes)
- • Rounds: AES-128 uses 10 rounds, AES-192 uses 12 rounds, AES-256 uses 14 rounds
- • Algorithm Structure: Based on Substitution-Permutation Network (SPN) structure
Security and Applications
- • Security Level: No effective cryptographic attack methods have been discovered to date
- • Government Certification: Adopted by the US government as the standard for classified information encryption
- • Commercial Applications: Widely used in banking, e-commerce, cloud storage, and other fields
- • Performance Advantages: Highly efficient in both hardware and software implementations
- • Standard Support: Supports multiple operation modes (ECB, CBC, CFB, OFB, CTR, etc.)
Recommended Use Cases
- • File and database encryption
- • Network communication encryption (HTTPS, VPN)
- • Mobile application data protection
- • Cloud storage security
DES (Data Encryption Standard)
Algorithm Overview
DES is a federal data processing standard adopted by the United States in 1977, and was the first publicly available modern symmetric encryption algorithm in history. Although it is now considered insufficiently secure, it holds significant importance in the history of cryptographic development.
Technical Characteristics
- • Key Length: 56-bit effective key (64-bit including 8-bit parity)
- • Block Size: 64 bits (8 bytes)
- • Rounds: 16-round Feistel network structure
- • Algorithm Structure: Based on Feistel cipher structure
Security Analysis
- • Security Issues: 56-bit key length is too short, vulnerable to brute force attacks
- • Historical Status: Officially declared insecure in 1999
- • Improved Version: 3DES provides better security
- • Current Status: Only suitable for non-critical data or educational demonstrations
Applicable Scenarios
- • Educational and research purposes
- • Legacy systems with compatibility requirements
- • Simple encryption of non-sensitive data
- • Cryptographic algorithm learning
Hash Functions (Digest Functions)
Algorithm Overview
Hash functions are one-way cryptographic functions that can convert input data of arbitrary length into fixed-length output values (hash values or digests). They possess important characteristics such as determinism, avalanche effect, and irreversibility, and are widely used for data integrity verification.
MD5 (Message Digest Algorithm 5)
- • Output Length: 128 bits (32 hexadecimal characters)
- • Release Date: 1992, designed by Ron Rivest
- • Security Status: Collision attacks have been discovered, not recommended for security scenarios
- • Applicable Scenarios: File verification, non-security hash requirements
- • Performance Characteristics: Fast computation speed, low resource consumption
SHA-1 (Secure Hash Algorithm 1)
- • Output Length: 160 bits (40 hexadecimal characters)
- • Release Date: 1995, designed by NSA
- • Security Status: Actual collisions discovered in 2017, now deprecated
- • Historical Status: Was the standard for protocols like SSL/TLS
- • Alternative Solutions: Recommend using SHA-256 or higher versions
SHA-256 (Secure Hash Algorithm 256)
- • Output Length: 256 bits (64 hexadecimal characters)
- • Release Date: 2001, member of SHA-2 family
- • Security Status: Currently secure, widely recommended for use
- • Application Areas: Bitcoin, SSL certificates, digital signatures
- • Performance Balance: Good balance between security and performance
SHA-512 (Secure Hash Algorithm 512)
- • Output Length: 512 bits (128 hexadecimal characters)
- • Release Date: 2001, member of SHA-2 family
- • Security Status: High security level, suitable for highly sensitive scenarios
- • Performance Characteristics: Excellent performance on 64-bit systems
- • Application Scenarios: Government and financial systems with high security requirements
HMAC (Hash-based Message Authentication Code)
Algorithm Overview
HMAC is a key-based hash computation message authentication code that combines hash functions with keys, providing both data integrity verification and message authentication functions. It is an algorithm defined by RFC 2104 standard.
Working Principle
- • Double Hashing: Performs two hash operations on the key and message
- • Key Processing: Uses inner and outer padding to process the key
- • Security Guarantee: HMAC may remain secure even if the hash function is compromised
- • Standardization: Adopted by multiple international standards
HMAC Variant Comparison
HMAC-SHA1
- • Output Length: 160 bits
- • Security Status: Not recommended for new projects due to SHA-1 weaknesses
- • Compatibility: Still used by some legacy systems
HMAC-SHA256
- • Output Length: 256 bits
- • Security Status: Currently recommended standard choice
- • Applications: JWT tokens, API signatures, OAuth
HMAC-SHA512
- • Output Length: 512 bits
- • Security Status: Highest security level
- • Suitable for: Enterprise-level applications with high security requirements
Base64 (Encoding Scheme)
Encoding Overview
Base64 is an encoding method that represents binary data using 64 printable characters. It is not an encryption algorithm, but an encoding scheme primarily used for transmitting binary data in text protocols.
Technical Features
- • Character Set:A-Z, a-z, 0-9, +, / (64 characters total)
- • Padding Character:Uses = for padding alignment
- • Encoding Ratio:Every 3 bytes encoded as 4 characters
- • Data Expansion:Encoded size is approximately 133% of original data
Application Scenarios
- • Email Transmission:Attachment encoding in MIME protocol
- • Web Development:Data URLs, image embedding
- • API Communication:Transmitting binary data in JSON
- • Configuration Files:Storing binary configuration information
- • Database:Storing binary fields
Important Notes
- • Base64 provides no security protection
- • Encoded data can be easily decoded
- • Should not be used for password or sensitive information protection
- • Primarily used for data transmission and storage compatibility
Security Usage Guidelines
Security Best Practices
- • Key Management:Use strong random keys, avoid simple or predictable keys
- • Key Isolation:Use different keys for different data, avoid key reuse
- • Key Storage:Store keys separately from encrypted data, use professional key management systems
- • Algorithm Selection:Prioritize AES-256 for highest security
- • Message Authentication:Use HMAC to ensure data integrity and authenticity
- • Key Protection:HMAC keys must be strictly confidential and regularly rotated
- • Transmission Security:Use secure channels (such as TLS) during key transmission
- • Regular Audits:Regularly review and update encryption implementations
Common Application Scenarios
Data Protection
- • File and database encrypted storage
- • User password hash verification
- • Sensitive configuration information protection
- • Backup data encryption
Network Communication
- • HTTPS/TLS secure communication
- • API request signature verification
- • JWT token authentication
- • Message queue data protection
Identity Authentication
- • Digital signatures and certificates
- • Two-factor authentication (2FA)
- • OAuth authorization flow
- • Single sign-on (SSO) systems
Compliance Requirements
- • GDPR data protection compliance
- • PCI DSS payment card data security
- • HIPAA medical data protection
- • Financial industry regulatory requirements