30 lines
911 B
Go
30 lines
911 B
Go
package cybersecurity
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import (
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"fmt"
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"golang.org/x/crypto/chacha20poly1305"
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)
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// OpenAEAD decrypts a ciphertext produced by SealAEAD using ChaCha20-Poly1305.
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// key must be exactly 32 bytes. nonce must match the one returned by SealAEAD.
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// aad must match what was passed to SealAEAD (can be nil).
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// Returns an error if authentication fails (tampered ciphertext, wrong key, or wrong aad).
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func OpenAEAD(key, nonce, ciphertext, aad []byte) ([]byte, error) {
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if len(key) != chacha20poly1305.KeySize {
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return nil, fmt.Errorf("open_aead: key must be %d bytes, got %d", chacha20poly1305.KeySize, len(key))
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}
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aead, err := chacha20poly1305.New(key)
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if err != nil {
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return nil, fmt.Errorf("open_aead: create cipher: %w", err)
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}
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plaintext, err := aead.Open(nil, nonce, ciphertext, aad)
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if err != nil {
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return nil, fmt.Errorf("open_aead: authentication failed: %w", err)
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}
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return plaintext, nil
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}
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