Combined Security Model: Digital Signature + Digital Envelope
An integrated model combining digital signatures and digital envelopes to secure authentication, integrity, and confidentiality across the full transmission path.
I. Overview
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flowchart LR
A["Authentication, integrity,\nand confidentiality handled separately"] -- "Combining digital signature + digital envelope" --> B["End-to-end\nintegrated security model"]
style A fill:#f9f9f9,stroke:#333,stroke-width:3px
style B fill:#e1f5fe,stroke:#01579b,stroke-width:3px
Definition: A mechanism that combines the authentication, integrity, and non-repudiation functions of a digital signature with the confidentiality function of a digital envelope to secure the entire transmission path.
Necessity:
( End-to-End Integrated Security ) Authentication, integrity, non-repudiation, and confidentiality are all secured simultaneously, completing protection across the full path
( Defense Against Sender Impersonation ) The digital signature verifies the sender’s identity, blocking impersonation by others at the source
( Prevention of Replay Attacks ) Combining a one-time session key with the signature defends against message reuse and tampering
II. Mechanism & Components
A. Sender-Side Processing (Sign-then-Encrypt)
graph TD
subgraph "Sender Process"
A["Original message"] -->|"Hash"| B["Message digest"]
B -->|"Encrypt with sender's private key"| C["Digital signature"]
A --- D["Combine original + digital signature"]
C --- D
D -->|"Encrypt with session key"| E["Encrypted data"]
F["One-time session key"] -->|"Encrypt with recipient's public key"| G["Digital envelope"]
end
E --- Final["[Ciphertext + digital envelope] final transmission"]
G --- Final
Detailed steps:
- Generate digital signature: The original message is hashed, then the digest is encrypted with the sender’s private key to produce a signature value
- Combine message: The digital signature is attached to the original message
- Encrypt data: The combined data is encrypted with a one-time symmetric key (session key)
- Generate digital envelope: The session key used is encrypted with the recipient’s public key to form the digital envelope
- Final transmission: [Encrypted data + digital envelope] is delivered to the recipient
B. Mapping to Security Functions
| Security Requirement | Implementing Technology | Detailed Mechanism |
|---|---|---|
| Confidentiality (C) | Digital envelope | Decryptable only via the session key, which is encrypted with the recipient’s public key |
| Integrity (I) | Hash function | If even a single bit of the message changes, the hash result changes |
| Authentication (A) | Digital signature | If the signature decrypts successfully with the sender’s public key, the sender’s identity is confirmed |
| Non-repudiation (N) | Asymmetric key | Because only the sender holds the private key used to sign, the sender cannot deny having sent the message |
III. Advanced Topics & Comparison
| Consideration | Details & Response Strategy |
|---|---|
| Computational Load | Asymmetric-key operations occur twice (signing, enveloping), so adopting a high-performance accelerator (HSM) should be considered |
| Certificate Validity | Before verifying a signature, certificate revocation status must always be checked first via the CRL or OCSP |
| Standard Protocols | Standardized mechanisms are used in S/MIME, PGP, and electronic tax-invoice systems |
Last updated 18 Aug 2026, 00:00 UTC.